ACTIVE ADAPTIVE HYDRAULIC RIPPLE CANCELLATION ALGORITHM AND SYSTEM

Abstract

Hydraulic pumps/motors are used to convert between rotational motion/power and fluid motion/power. Pressure differential is achieved across the pump/motor by applying torque to either aid or impede rotation which generally results in either a pressure rise or pressure drop respectively across the unit. This torque is often supplied by an electric motor/generator. Especially in positive displacement pumps/motors this pressure differential is not a smooth value but rather it contains high frequency fluctuations known as pressure ripple that are largely undesirable. With thorough analysis it can be discovered that these fluctuations occur in a predictable manner with respect to the position (angular or linear) of the pump/motor. Using a model that contains this information, a feed-forward method of high-frequency motor torque control is implemented directly on the hydraulic pump/motor by adding to the nominal torque, a model-based torque signal that is linked to rotor position. This high-frequency signal acts directly on the hydraulic pump/motor to reduce or cancel the pressure/flow ripple of the pump/motor itself without the need for any secondary flow generating devices.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT application serial number PCT/US2014/029654, entitled “ACTIVE VEHICLE SUSPENSION IMPROVEMENTS”, filed Mar. 14, 2014, which claims the priority under 35 U.S.C. §119(e) of U.S. provisional application Ser. No. 61/913,644, entitled “WIDE BAND HYDRAULIC RIPPLE NOISE BUFFER”, filed Dec. 9, 2013, U.S. provisional application Ser. No. 61/865,970, entitled “MULTI-PATH FLUID DIVERTER VALVE”, filed Aug. 14, 2013, U.S. provisional application Ser. No. 61/815,251, entitled “METHOD AND ACTIVE SUSPENSION”, filed Apr. 23, 2013, and U.S. provisional application Ser. No. 61/789,600, entitled “IMPROVEMENTS IN ACTIVE SUSPENSION”, filed Mar. 15, 2013 , the disclosures of which are incorporated by reference in their entirety.

BACKGROUND

1. Field

Aspects relate to a device and methods for electronically attenuating pressure and or flow ripple in positive displacement hydraulic pumps/motors.

2. Discussion of Related Art

Typically in positive displacement hydraulic pumps/motors pressure differential generated by constant torque application contains pressure ripple that is largely undesirable. This ripple is typically the result of non-constant flow capacity of the hydraulic pump/motor and of the variable leakage path around the pump/motor as a function of the position. It also typically occurs at frequencies related to the speed of the pump. For a rotary pump such as a form of gear pump, this ripple occurs at a frequency that is equal to the rotational frequency of the unit multiplied by the number of teeth or lobes and in integer harmonics thereof. For a piston-type pump the ripple frequency is proportional to the stroke period of individual pistons multiplied by the total number of pistons.

Methods of reducing the magnitude of this ripple may commonly include increasing the number of ripple pulses per hydraulic cycle (e.g. number of gear teeth, number of pistons) or dampening the ripple downstream or upstream of the pump/motor by some means such as adding compliance. This may be accomplished by inserting a device such as an accumulator. Other methods of reducing the pressure ripple of hydraulic pumps/motors may include an apparatus for sensing the flow ripple generated by the pump and counteracting this with a negative ripple generator to cancel and eliminate the system flow ripple, where the negative ripple generator consists of a moveable piston controlled by a solid state motor.

These arrangements require a second flow control source (e.g. the piston) in order to function, resulting in a complex system with multiple electronically controlled devices. This arrangement also requires direct measurements of the flow or pressure ripple to perform closed loop feedback control of the secondary flow source, resulting in a more expensive system. Another method of reducing the flow ripple in a hydraulic system includes using a hydrostatic motor in fluid communication with a variable displacement pump. In this arrangement a displacement signal is generated and applied to the variable displacement unit in order to reduce the torque ripple of the hydrostatic motor. This arrangement also has the negative attribute of requiring multiple independently controlled hydraulic flow generating devices. It is recognized that the ability to substantially attenuate the ripple of a hydraulic pump/motor without the need for additional flow generating devices, at a broad spectrum of frequencies with minimal cost and minimal efficiency penalties, is highly desirable.

SUMMARY

Aspects of the invention relate to a device and methods to electronically control and improve the ripple characteristics of hydraulic pumps/motors. Subsequent references to a hydraulic pump will be synonymous with a hydraulic pump and with a hydraulic motor. Subsequent references to an electric motor will be synonymous with an electric motor and with an electric generator and with a BLDC motor. References to a rotor and position thereof are synonymous with the entire rotating assembly and therefore with the electric motor position and hydraulic pump position. Subsequent references to ripple torque and ripple velocity are synonymous with a torque signal that is commanded by the controller and with a velocity signal commanded by the controller respectively; both are cancellation signals that are added to a nominal command torque or velocity signal. Subsequent references to steady state conditions are synonymous with a substantially constant hydraulic pump velocity. Subsequent references to displacement flow are synonymous with flow that is transported through the hydraulic pump/motor. This displacement flow may vary with the angular position of the rotor. An operating point may be specified by a combination of pressure differential and pump velocity.

According to one aspect, a hydraulic pump is coupled to the shaft of an electric motor such that torque applied to the shaft of the electric motor results in torque applied to the hydraulic pump. A method of electric motor position sensing is provided such that accurate control over motor torque with respect to position is achieved. Pressure differential is generated across the hydraulic pump by applying torque to the shaft of the electric motor. This torque can be either a retarding torque, in which case shaft power is extracted from the pressure differential, or a driving torque, in which case power is input to the electric motor to cause a pressure differential. Normally, constant application of torque at steady state will generate non-constant and periodic fluctuations in pressure differential due predominately to the geometric nature of the hydraulic pump and non-constant flow capacity therein; this fact is well known by those trained in the art. With proper analysis it can be discovered that these fluctuations occur in a predictable manner with respect to the position (angular or linear) of the pump and at a frequency proportional to the rotational speed of the pump. To counteract these natural fluctuations in pressure, a non-constant torque, or ripple torque, can be carefully applied as a function of rotor position by the electric motor in order to attenuate the magnitude of the generated pressure ripple. This torque may fluctuate above and below the nominal mean constant torque to achieve the same mean pressure as the above-mentioned case of constant torque application. In this manner the mean of the ripple torque may be the same value as the constant torque to achieve the same mean pressure differential. Typically, one revolution of the hydraulic motor will generate a predetermined and predictable number of periodic fluctuations in pressure and/or flow, which in steady state operation will comprise a periodic waveform with respect to position. In order to correctly apply torque to achieve this behavior, the position dependent nature of the ripple and therefore the position dependent requirements of ripple torque application must be known or discovered. The ripple torque may result in a ripple velocity to increase velocity and generate increased displacement flow when the displacement flow is lower than the mean flow, and to decrease velocity and generate decreased displacement flow when the displacement flow is higher than the mean flow.

According to one aspect the ripple torque applied is commanded of the controller by a ripple model that includes rotor position. The ripple model specifies the waveform of ripple torque to be applied in order to attenuate pressure ripple at a given operating point. The specification of the torque waveform may include the magnitude of one or more periodic waveforms, relative phase angles between each of the plurality of waveforms, as well as the relative phase angle of the resultant waveform with respect to position of the electric motor. The summation of one or a plurality of waveforms with predominant frequencies with respect to rotor position at any integer harmonic may produce a resultant waveform that serves to attenuate pressure ripple at multiple harmonic frequencies of the primary rotational frequency.

In one embodiment the mean ripple torque applied in order to achieve a substantially constant pressure differential value is substantially equal to the constant torque value applied to achieve a mean pressure ripple of the same value. The root mean square value of the ripple torque may be higher than the mean ripple torque. In this manner the additional electric power losses associated with this method of ripple cancellation are a result of the electrical resistance losses due to the difference between the root mean square current and the mean current required to produce the tipple current. This may be considered small in comparison with the overall electrical resistance losses and therefore negligible as a loss of the system.

In one embodiment the ripple model takes as direct inputs any of rotor velocity, electric motor torque, hydraulic flow rate, and hydraulic pressure. An operating point may be determined by a combination of rotor velocity or hydraulic flow rate, and motor torque or hydraulic pressure. The model may be a function or a series of functions in which the direct inputs serve as independent variables. The model may otherwise be a multidimensional array indexed by any combination of the direct inputs.

In one embodiment the parameters of the ripple model with either of the above detailed formulations are adaptable and or updatable. Sensor input from one or a plurality of secondary sensors that are not used to detect rotor position are used as feedback to the ripple model in order to update model parameters that specify the ripple torque waveform. In this manner the model need not account for all effects of externalities and perturbations but rather, may dynamically update its parameters to account for these factors as they relate to the hydraulic pressure ripple and the corresponding cancellation waveform.

In one embodiment, the ripple model is a feed-forward ripple model of any of torque and velocity. The inputs to the model are based on commanded or sensed parameters while the system response is not monitored as a feedback signal. In this manner the model does not have a measure of its performance and does not dynamically adjust its output accordingly to system response in a time scale on the order of the system time constant.

In one embodiment ripple cancellation is carried out in a closed loop feedback based control system. A sensor that correlates with pressure ripple (a pressure sensor, a flow sensor, a strain gauge, an accelerometer etc.) is used to feed back the ripple response and compare it to a desired output, which may be based on an input parameter (pressure, flow, force etc.), the difference between the desired and actual being considered the error or ripple. This signal is then fed into the motor controller, which adjusts the applied torque in order to minimize the magnitude of the ripple signal.

In one embodiment rotor position may be detected by any of a number of methods including a rotary encoder, a Hall effect sensor, optical sensors, or model-based position estimation that utilize external signals such as phase voltages and phase current signals of the electric motor. The latter are known in the field as “sensor-less” algorithms for controlling electric motors. Sensor-less methods may include comparing electric motor parameters to a model of motor back EMF.

In one embodiment the output of the ripple model is a specified ripple velocity as opposed to a ripple torque. At constant velocity the displacement flow of the hydraulic pump is non-constant so it may be necessary for the speed to ripple accordingly. In this manner the motor controller performs closed-loop velocity control in order to achieve the ripple velocity specified by the ripple model. No ripple torque specification is necessary and no feedback on torque is performed. The output of a ripple velocity has the same attenuation effect on pressure ripple as the model that specifies ripple torque. The factors that influence how ripple torque leads to a ripple velocity primarily include hydraulic drag torque and rotational inertia. The primary difference of a ripple velocity model over a ripple torque model is that these influences and changes therein are external to the model set parameters and are instead accounted for in the closed loop velocity control. Any changes in torque requirements to achieve a specified ripple velocity will be directly handled by the velocity feedback control.

In one embodiment the electric motor is immersed in a hydraulic fluid along with the hydraulic pump. In this manner position sensing of the electric motor must be performed inside a pressurized fluid environment. The hydraulic pump is preferably located coaxially with the electric motor.

In one embodiment the electric motor and hydraulic pump are contained in an actuator of a vehicle suspension system. Pressure differential generated across the hydraulic pump results in a force on the piston of the actuator. Command torque on the electric motor may be the output of a separate vehicle dynamics model and or feedback control system. The ripple torque may be added to the command torque to impart an overall torque applied to the rotor. In the event that a ripple velocity model is used, the command torque is used to specify the mean pressure, which may be used as an input to the ripple velocity model.

In one embodiment, operating the electric motor comprises adjusting the current flow through the windings of the electric motor in response to sensed angular position of the rotor. Operating the electric motor may also be accomplished by adjusting the voltage in the windings of the electric motor in response to sensed angular position of the rotor. The electric motor may be a BLDC motor.

It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing, and some similar components may have different numbers. In the drawings:

FIG. 8-1 is a representative plot of hydraulic pump/motor pressure ripple about a nominal average pressure under constant electric motor/generator torque.

FIG. 8-2A is a representative plot of hydraulic pump/motor pressure ripple about a nominal average pressure under constant electric motor/generator torque over one repeating hydraulic pump/motor cycle.

FIG. 8-2B is a representative plot of hydraulic pump/motor pressure ripple about a nominal average pressure under fluctuating and controlled motor/generator torque over the same repeating hydraulic pump/motor cycle as 8-2A. The fluctuating torque compensates natural pressure variations in the hydraulic system thereby attenuating the resulting system pressure fluctuations.

FIG. 8-3A is a representative plot of the necessary electric motor/generator torque to produce the pressure ripple shown in FIG. 1A.

FIG. 8-3B is a representative plot of the necessary electric motor/generator torque to produce the attenuated pressure ripple shown in FIG. 1B.

FIG. 8-4 is an embodiment of the control block diagram of a model-based feed-forward ripple cancelling control system for a hydraulic pump/motor with rotor position sensing. (The nominal torque command may be the output of a vehicle control model.)

FIG. 8-5 is an embodiment of the control block diagram of a feedback based ripple cancelling torque control system for a hydraulic pump/motor based on load feedback (pressure, force, acceleration etc.). (The nominal pressure/force/acceleration command may be the output of a vehicle control model.)

FIG. 8-6 is an embodiment of the control block diagram of an adaptable model-based feed-forward torque ripple canceling control system for a hydraulic pump/motor. External sensors provide input to the controller and the model is updated semi-continuously during the course of operation. Direct feedback control is not implemented.

DETAILED DESCRIPTION

Some aspects relate to a system and feed-forward control method of electronically attenuating pressure ripple in a positive displacement pump/motor. Other aspects relate to a method of adapting a model based feed-forward control on the basis of output sensor information.

Regarding FIG. 8-1, a representative plot of steady state pressure ripple in the time domain is shown for a hydraulic pump/motor operating at constant frequency under a constant torque application. A generated pressure differential signal 8-102 fluctuates in time about a mean pressure differential 8-104 which is substantially constant throughout time. The peak-to-peak amplitude 8-106 of this fluctuating pressure differential signal 8-102 is substantially consistent throughout time as the geometric pattern of the hydraulic pump/motor is symmetric. The peak-to-peak amplitude 8-106 is determined by many characteristics of the hydraulic pump.

In FIG. 8-2A a representative plot of steady state pressure ripple in the position domain is shown for a hydraulic pump operating at constant frequency under a constant torque application. The position theta 8-202 defines the geometric period in position over which the pump is geometrically repeating; the average periodic pressure ripple 8-204 over this position period is consistent. The mean pressure differential 8-206 is substantially constant over one periodic cycle and therefore constant throughout operation. The peak-to-peak amplitude 8-106 of the fluctuating pressure signal is consistent from cycle to cycle as the system is nominally periodic in geometry.

In FIG. 8-2B a representative plot of pressure ripple in the position domain is shown for a pump/motor under torque application from a model based feed forward torque controller. The mean pressure differential 8-206 remains at the same value as in FIG. 8-2A. The peak-to-peak amplitude 8-108 of the fluctuating pressure signal 8-210 is consistent from cycle to cycle and is considerably smaller than the peak-to-peak amplitude 8-106 in the constant torque application case of FIG. 8-2A. The average repeating pressure ripple 8-210 retains periodicity over the same geometric period theta 8-202.

In FIG. 8-3A a steady state time domain representation of the constant torque application to achieve the pressure ripple in FIG. 8-2A is shown. The torque value 8-302 is constant throughout time and is a DC value with some offset from zero.

In FIG. 8-3B a steady state time domain representation of a fluctuating torque output from a model-based feed forward controller is shown. The mean torque 8-304 is constant throughout time and equal to the constant torque 8-302 from the case shown in FIG. 8-3A. The torque signal 8-306 fluctuates above and below the mean torque 8-304. The peak-to-peak amplitude 8-308 of the torque signal has a magnitude that is an output of the ripple model.

In FIG. 8-4 a control block diagram of a model-based feed-forward ripple cancelling torque control system for a hydraulic pump is shown. A nominal torque command 8-402, which is an output of a separate system level control system, is an input to the feed-forward ripple model 8-404. Along with the nominal torque command 8-402, the rotational speed of the hydraulic pump 8-424 is fed into the feed-forward ripple model 8-404 which in turn outputs a ripple torque magnitude 8-406 and a ripple torque phase offset 8-408 with respect to rotor position 8-422. The ripple torque magnitude 8-406 and ripple torque phase offset 8-408 are fed into the motor controller 8-410 which also takes as input the nominal torque command 8-402 and in turn outputs an overall applied torque 8-412 to the system 8-414 which refers to the hydraulic pump. The applied torque 8-412 results in a generated pressure differential 8-416 across the hydraulic pump 8-414 as well as a rotational speed 8-418 of the hydraulic pump. A position sensor 8-420 monitors the position 8-422 of the pump 8-414 from which rotor speed 8-424 can be derived. The resulting rotor speed 8-424 is again fed into the feed-forward ripple model 8-404. Note that the control variable of interest in this system is pressure differential 8-416 yet there is no corresponding pressure sensor or feedback on this signal.

In FIG. 8-5 a control block diagram of a closed-loop feedback based ripple cancelling torque control system is shown. The motor controller 8-502 outputs an applied torque 8-504, which acts on the system 8-506, which refers to the hydraulic pump. The torque applied 8-504 results in a rotational speed 8-508 of the hydraulic pump system 8-506 as well as a generated pressure differential 8-510 across the pump 8-506. A pressure sensor 8-512 feeds the pressure differential signal 8-510 into a block where it is summed with a nominal pressure differential command 8-514 which itself is an output of a separate system level control system. The result of this summation or subtraction is the error of the system or the hydraulic ripple 8-516. This ripple 8-516 is fed into the motor controller 8-502 which in turn adjusts its applied torque 8-504 in order to minimize the magnitude of the ripple 8-516.

In FIG. 8-6 a control block diagram of an adaptive mode-based feed-forward ripple cancelling torque control system for a hydraulic pump is shown. A nominal torque command 8-602, which is an output of a separate system level control system, is an input to the feed-forward ripple model 8-604. Along with the nominal torque command 8-602, the rotational speed of the pump 8-624 is fed into the feed-forward ripple model 8-604 which in turn outputs a ripple torque magnitude 8-606 and a ripple torque phase offset 8-608 with respect to pump position. The ripple torque magnitude 8-606 and ripple torque phase offset 8-608 are fed into the motor controller 8-610 which also takes as input the nominal torque command 8-602 and the motor position 8-622 and in turn outputs an overall torque applied 8-612 to the system 8-614 which refers to the hydraulic pump. The torque applied 8-612 results in a generated pressure differential 8-616 across the hydraulic pump system 8-614 as well as a rotational speed 8-618 of the hydraulic pump 8-614. A position sensor 8-620 monitors the position 8-622 of the pump/motor 8-614 from which rotor speed 8-624 can be calculated. The resulting speed 8-624 is again fed into the feed-forward ripple model 8-604. External sensors 8-626, which monitor system, ripple response but are not directly used in closed-loop feedback are fed into and used to update and adapt the feed-forward ripple model 8-604. This updating may generally occur over a time period that is substantially longer than the time constant of the system.

Claims

1. A method of hydraulic ripple cancellation, comprising:

sensing an angular position of a rotor of an electric motor;

operatively coupling the electric motor to a hydraulic pump; and

operating the electric motor to impart at least one of a command torque and a command velocity on the hydraulic pump and to impart at least one of a ripple torque and a ripple velocity on the hydraulic pump based at least in part on the sensed angular position of the rotor.

2. The method of claim 1, wherein the hydraulic ripple is at least one of pressure ripple and fluid flow ripple.

3. The method of claim 1, wherein the at least one of ripple torque and ripple velocity is a variable at least one of torque and velocity that is imparted based on at least one of current electric motor torque and speed.

4. The method of claim 1, wherein the at least one of ripple torque and ripple velocity substantially comprises a periodic waveform.

5. The method of claim 4, wherein the periodic waveform comprises one or more sine waves.

6. The method of claim 4, wherein the periodic waveform comprises a plurality of waveforms, each having a period, magnitude, and shape.

7. The method of claim 4, wherein the periodic waveform at least partially cancels one or more harmonics of the hydraulic ripple.

8. The method of claim 1, wherein the electric motor velocity is electrically varied based at least in part on the sensed angular position of the rotor.

9. The method of claim 1, wherein the hydraulic pump at a constant speed is characterized by a varying flow rate with respect to angular position, and wherein at least one of torque and velocity of the electric motor is electrically controlled to compensate for this non-constant flow property.

10. The method of claim 1, wherein sensing of angular rotor position is accomplished by one of a rotary encoder, hall effect sensor, and sensorless control using phase voltages and currents of the electric motor.

11. The method of claim 1, wherein the at least one of ripple torque and ripple velocity is imparted based on a model of at least one of torque and velocity control that includes rotor position.

12. The method of claim 11, wherein the model of at least one of torque and velocity is feed-forward.

13. The method of claim 11, wherein the model of at least one of torque and velocity adapts parameters based on one or more feedback sensors.

14. The method of claim 13, wherein the feedback sensor is one of an accelerometer and a pressure sensor.

15. The method of claim 11, wherein the model of at least one of torque and velocity control comprises one of a function and a multidimensional array.

16. The method of claim 11, wherein independent variables in the model comprise of at least one of rotor velocity, motor torque, and hydraulic pressure.

17. The method of claim 11, wherein the model of at least one of torque and velocity control outputs one or more magnitude and phase values that specify the ripple cancellation waveform.

18. The method of claim 11, wherein the model of at least one of torque and velocity control comprises a multidimensional array that represents at least one of ripple torque and ripple velocity parameters for a plurality of rotor speeds.

19. The method of claim 1, wherein operating the electric motor includes receiving input from a second sensor that detects conditions other than an angular position of the rotor and factoring that input from the second sensor into imparting at least one of the command at least one of torque and velocity and the at least one of ripple torque and ripple velocity.

20. The method of claim 1, wherein the electric motor is a BLDC motor.

21. The method of claim 1, wherein the electric motor is immersed in a hydraulic fluid with the hydraulic pump.

22. The method of claim 1, wherein coupling the electric motor to the hydraulic pump comprises disposing the electric motor coaxially with the hydraulic pump.

23. The method of claim 1, wherein operating the electric motor comprises adjusting current flow through windings of the electric motor in response to the sensed angular position of the rotor of the electric motor.

24. The method of claim 1, wherein operating the electric motor comprises adjusting voltage in the windings of the electric motor in response to the sensed angular position of the rotor of the electric motor.

25. The method of claim 1, wherein operating the electric motor comprises receiving input from a plurality of feedback sensors that sense impact of the imparted at least one of torque and velocity on a hydraulic fluid that engages the hydraulic pump.

26. A method of hydraulic ripple cancellation, comprising:

sensing an angular position of a rotor of an electric motor;

operatively coupling the electric motor to a hydraulic pump; and

operating the electric motor to comply with a at least one of torque and velocity control model of hydraulic pump that facilitates mitigation of hydraulic ripple associated with fluid flow and pressure changes during rotation of the hydraulic pump, based on the sensed angular position of the rotor.

27. The method of claim 26, wherein operating the electric motor comprises imparting a command at least one of torque and velocity on the hydraulic pump and imparting a at least one of ripple torque and ripple velocity on the hydraulic pump based at least in part on the sensed angular position of the rotor.

28. The method of claim 27, wherein the at least one of ripple torque and ripple velocity at least partially cancels hydraulic ripple associated with fluid flow and pressure changes.

29. The method of claim 26, wherein the control model comprises one of a function and a multidimensional array.

30. The method of claim 26, wherein the control model includes motor torque and speed as inputs.

31. The method of claim 26, wherein the control model adapts parameters based on one or more feedback sensors.

32. The method of claim 31, wherein the one or more feedback sensors comprises one of an accelerometer and a pressure sensor.

33. A system comprising:

a motor controller adapted to dynamically control an electric motor that is operatively coupled to a hydraulic pump and adapted to receive a command input; and

a control algorithm that facilitates the motor controller determining a at least one of ripple torque and ripple velocity factor based on a detected position of a rotor of the electric motor, wherein the motor controller imparts at least one of torque and velocity control on the hydraulic pump through the electric motor, the at least one of torque and velocity control comprising a command input component and a at least one of ripple torque and ripple velocity component.

34. The system of claim 33, wherein the ripple component is at least one of a torque component and a velocity component.

35. The system of claim 33, wherein the command input component is at least one of a torque component and a velocity component.

36. The system of claim 33, wherein the hydraulic pump creates a hydraulic ripple comprising at least one of a pressure ripple and a fluid flow ripple, and the at least one of ripple torque and ripple velocity imparted on the hydraulic pump is substantially out of phase with the hydraulic ripple.

37. The system of claim 33, wherein the hydraulic pump is at a constant speed and is characterized by a varying flow rate with respect to angular position, and wherein at least one of torque and velocity of the electric motor is electrically controlled to compensate for this non-constant flow property.

38. The system of claim 33, wherein the at least one of ripple torque and ripple velocity is a variable of at least one of torque and velocity that is imparted based on at least one of current electric motor torque and current electric motor speed.

39. The system of claim 33, wherein the at least one of ripple torque and ripple velocity substantially comprises a periodic waveform.

40. The system of claim 39, wherein the periodic waveform comprises one or more sine waves.

41. The system of claim 39, wherein the periodic waveform comprises a plurality of waveforms, each having a period, magnitude, and shape.

42. The system of claim 39, wherein the periodic waveform at least partially cancels one or more harmonics of the hydraulic ripple.

43. The system of claim 33, wherein electric motor velocity is electrically varied based at least in part on the sensed angular position of the rotor.

44. The system of claim 33, further comprising a rotor position sensor that is one of a rotary magnetic/optical encoder and a Hall effect sensor.

45. The system of claim 33, further comprising a plurality of voltage and current sensors measuring currents and voltages of the electric motor, with an algorithm detecting rotor position using sensorless control.

46. The system of claim 33, wherein the at least one of ripple torque and ripple velocity is imparted based on a model of at least one of torque and velocity control.

47. The system of claim 46, wherein the model of at least one of torque and velocity is feed-forward.

48. The system of claim 46, wherein the model of at least one of torque and velocity adapts parameters based on one or more feedback sensors.

49. The system of claim 48, wherein the feedback sensor is one of an accelerometer and a pressure sensor.

50. The system of claim 46, wherein the model of at least one of torque and velocity control comprises one of a function and a multidimensional array.

51. The system of claim 46, wherein independent variables in the model comprise of at least one of rotor velocity, motor torque, and hydraulic pressure.

52. The system of claim 46, wherein the model of at least one of torque and velocity control outputs one or more magnitude and phase values that specify the ripple cancellation waveform.

53. The system of claim 46, wherein the model of at least one of torque and velocity control comprises a multidimensional array that represents at least one of ripple torque and ripple velocity parameters for a plurality of rotor speeds.

54. The system of claim 33, wherein operating the electric motor includes receiving input from a second sensor that detects conditions other than an angular position of the rotor and factoring that input from the second sensor into imparting at least one of the command at least one of torque and velocity and the at least one of ripple torque and ripple velocity.

55. The system of claim 33, wherein the electric motor is a BLDC motor.

56. The system of claim 33, wherein the electric motor is immersed in a hydraulic fluid with the hydraulic pump.

57. The system of claim 33, wherein coupling the electric motor to the hydraulic pump comprises disposing the electric motor coaxially with the hydraulic pump.

58. The system of claim 33, wherein operating the electric motor comprises receiving input from a plurality of feedback sensors that sense impact of the imparted at least one of torque and velocity on a hydraulic fluid that engages the hydraulic pump.

59. A system comprising:

an electro-hydraulic actuator of a vehicle suspension system comprising a motor controller adapted to dynamically control an electric motor that is operatively coupled to a hydraulic pump and adapted to receive a command input; and

a control algorithm that facilitates the motor controller determining a ripple torque factor based on a detected position of a rotor of the electric motor, wherein the motor controller imparts at least one of torque and velocity control on the hydraulic pump through the electric motor, the at least one of torque and velocity control comprising a command component and a at least one of ripple torque and ripple velocity component.

60. The system of claim 59, wherein the command component is at least one of a torque component and velocity component.

61. The system of claim 59, wherein the ripple component is at least one of a torque component and a velocity component.

62. The system of claim 59, wherein the hydraulic pump creates a hydraulic ripple comprising at least one of a pressure ripple and a fluid flow ripple, and the at least one of ripple torque and ripple velocity imparted on the hydraulic pump is substantially out of phase with the hydraulic ripple.

63. The system of claim 59, wherein the hydraulic pump is at a constant speed and is characterized by a varying flow rate with respect to angular position, and wherein at least one of torque and velocity of the electric motor is electrically controlled to compensate for this non-constant flow property.

64. The system of claim 59, wherein the at least one of ripple torque and ripple velocity is a variable of at least one of torque and velocity that is imparted based on at least one of current electric motor torque and speed.

65. The system of claim 59, wherein the at least one of ripple torque and ripple velocity substantially comprises a periodic waveform.

66. The system of claim 65, wherein the periodic waveform comprises one or more sine waves.

67. The system of claim 65, wherein the periodic waveform comprises a plurality of waveforms, each having a period, magnitude, and shape.

68. The system of claim 65, wherein the periodic waveform at least partially cancels one or more harmonics of the hydraulic ripple.

69. The system of claim 59, wherein electric motor velocity is electrically varied based at least in part on the sensed angular position of the rotor.

70. The system of claim 59, further comprising a rotor position sensor that is one of a rotary magnetic/optical encoder and a Hall effect sensor.

71. The system of claim 59, further comprising a plurality of voltage and current sensors measuring currents and voltages of the electric motor, with an algorithm detecting rotor position using sensorless control.

72. The system of claim 59, wherein the at least one of ripple torque and ripple velocity is imparted based on a model of at least one of torque and velocity control.

73. The system of claim 72, wherein the model of at least one of torque and velocity is feed-forward.

74. The system of claim 72, wherein the model of at least one of torque and velocity adapts parameters based on one or more feedback sensors.

75. The system of claim 74, wherein the one or more feedback sensors comprises one of an accelerometer and a pressure sensor.

76. The system of claim 72, wherein the model of at least one of torque and velocity control comprises one of a function and a multidimensional array.

77. The system of claim 72, wherein independent variables in the model comprise of at least one of rotor velocity, motor torque, and hydraulic pressure.

78. The system of claim 72, wherein the model of at least one of torque and velocity control outputs one or more magnitude and phase values that specify the ripple cancellation waveform.

79. The system of claim 72, wherein the model of at least one of torque and velocity control comprises a multidimensional array that represents at least one of ripple torque and ripple velocity parameters for a plurality of rotor speeds.

80. The system of claim 59, wherein operating the electric motor includes receiving input from a second sensor that detects conditions other than an angular position of the rotor and factoring that input from the second sensor into imparting at least one of the command at least one of torque and velocity and the at least one of ripple torque and ripple velocity.

81. The system of claim 59, wherein the electric motor is a BLDC motor.

82. The system of claim, wherein the electric motor is immersed in a hydraulic fluid with the hydraulic pump.

83. The system of claim 59, wherein coupling the electric motor to the hydraulic pump comprises disposing the electric motor coaxially with the hydraulic pump.

84. The system of claim 59, wherein operating the electric motor comprises receiving input from a plurality of feedback sensors that sense impact of the imparted at least one of torque and velocity on a hydraulic fluid that engages the hydraulic pump.

85. A method of hydraulic ripple cancellation, comprising:

measuring a sensor that correlates with pressure ripple in a hydraulic system;

operatively coupling an electric motor to a hydraulic pump that induces the hydraulic ripple; and

operating the electric motor to impart a command at least one of torque and velocity component on the hydraulic pump and to impart a at least one of ripple torque and ripple velocity component on the hydraulic pump based at least in part on the sensed pressure ripple in the hydraulic system.

86. The method of claim 85, wherein the command component is at least one of a torque component and velocity component.

87. The method of claim 85, wherein the ripple component is at least one of a torque component and a velocity component.

88. The method of claim 85, wherein the sensor that correlates with pressure ripple comprises at least one of a pressure sensor, a flow rate sensor, a strain gauge, and an accelerometer disposed on the hydraulic system.