Vibration control system and improvements in or relating to skis
Vibration control systems are described which provide for the variation in stiffness and damping in a structure. The systems are based on the use of rheological fluid, with examples provided of magnetorheological fluid flex actuators and semi-active damping systems. An adaptive vibration control system is also described incorporating sensors, a signal processor and a power supply together with the fluid flex actuators and semi-active damping systems. Embodiments are described for use in and with skis.
The present invention relates to vibration control systems and in particular, though not exclusively, to an adaptive control system to vary flex and damping in skis during use.
It is known that vibration of an object can be suppressed in objects manufactured with a calculated stiffness and damping. However, when the object is subjected to a range of operating conditions the frequency of vibration can vary i.e. the bandwidth increases. Objects having a fixed stiffness and damping cannot suppress vibration at varying frequencies and as a result the object is prone to vibration with deleterious effect.
An area where vibration reduces performance is in skiing. Vibration causes a ski to ‘chatter’ and so loose edge contact. Manufacturers have engineered skis by varying geometry, materials and construction techniques in an effort to suppress vibration, but such skis tend to be limited to use in certain environments. For example, male downhill race skiers use skis which have a high stiffness whereas recreational skiers have more flexible skis. It is recognised that it would be advantageous to provide a ski in which the stiffness and damping could be varied during use and so improve the handling of a ski in a range of environments.
It is an object of at least one embodiment of the present invention to provide a vibration control system which includes active flex control to vary the stiffness of an object during use.
It is a further object of at least one embodiment of the present invention to provide a vibration control system which includes a semi-active damping system to change the damping level so as to optimally counteract motion with a controlled resistive motion.
It is a yet further object of at least one embodiment of the present invention to provide a vibration control system which automatically adapts to surrounding conditions to provide active vibration control.
It is an object of at least one embodiment of the present invention to provide a ski including active flex control.
It is a further object of at least one embodiment of the present invention to provide a ski including a semi-active damping system.
It is a yet further object of at least one embodiment of the present invention to provide a ski having automatic adaptive control of stiffness and damping during use.
According to a first aspect of the present invention there is provided a vibration control system, the system comprising a structure including a chamber and a means for creating a variable applied field within the chamber, wherein the chamber is substantially filled with a rheological fluid which under the influence of the applied field causes a variation in the stiffness of the structure.
The rheological fluid may be an electrorheological fluid which undergoes a change in viscosity proportional to a change in electric field. Advantageously the rheological fluid is a magnetorheological fluid which undergoes a change in viscosity proportional to a change in applied magnetic field.
Preferably the applied field is a continuously variable applied field.
Preferably, the means for creating a variable applied field comprises an electromagnetic coil. A variable power source may be applied to the coil.
The structure may include a first member having a first surface and a second member having a second surface, the surfaces being inner walls of the chamber and are arranged to face each other, wherein the rheological fluid is located therebetween such that in the presence of the applied field, a shear force is set-up between the surfaces by virtue of the fluid which varies the stiffness of the structure.
Alternatively, the structure may include a piston moveable within the chamber. Preferably the piston is an electromagnet such that the magnetic field strength may be varied within the chamber. More preferably, the piston is hollow providing a fluid flow path therethrough. Thus as the magnetic field strength is increased, the fluid particles in the piston align. This results in an apparent increase in viscosity that reduces the ability of the fluid to flow through the piston. Therefore by increasing the magnetic field, resistance to flow reduces the flex and hence increases the stiffness of the structure. The converse is also true. This vibration control system may be referred to as a resistive flow active flex system.
According to a second aspect of the present invention there is provided a vibration control system, the system comprises a mounting surface upon which is located a flexible hose, the hose having a first cross-sectional area filled with a rheological fluid and ends abutted to the surface.
The system provides semi-active damping as any flexing of the mounting surface will create a change in the cross-sectional area of the hose and cause the hose to act as a pump, while application of an applied field will cause the fluid to act as a valve. Consequently, an increase in field increases the fluid viscosity, the valve makes it more difficult to pump the fluid and thus more force is required to flex the hose, providing a damping effect.
The rheological fluid may be an electrorheological fluid which undergoes a change in viscosity proportional to a change in electric field. Advantageously the rheological fluid is a magnetorheological fluid which undergoes a change in viscosity proportional to a change in applied magnetic field.
Preferably the rheological fluid is ‘Rheonetic Fluid’ as produced by Lord Corporation, USA.
Preferably a plurality of hoses are located on the surface. More preferably the hoses are located symmetrically on the surface.
According to a third aspect of the present invention there is provided an adaptive vibration control system, the system comprising sensing means to determine one or more environmental characteristics, a signal processor to determine a controlling response to the characteristics and vibration control means responsive to the controlling response to counter vibration.
Preferably the sensing means is at least one sensor. More preferably the sensing means is a multi-sensor array. Advantageously the sensor array is a distributed array of PVDF piezo-sensors.
Preferably the signal processor identifies characteristic vibration patterns from the sensors. The signal processor may also include a control algorithm to identify the patterns. Preferably also the signal processor includes a feedback loop from the vibration control means to regulate the response.
Advantageously, the signal processor is a microprocessor. More preferably, the microprocessor is a proportional-differential-integral processor. Advantageously, the control algorithm is a fuzzy logic control algorithm to provide an intelligent control unit. Such an intelligent control unit with a fuzzy logic control algorithm programmed into the microprocessor may grade the vibration being monitored and control a graded response from the vibration control means.
Preferably the vibration control means comprises a vibration control system according to the first aspect. Preferably also the vibration control means comprises a vibration control system according to the second aspect. Advantageously the controlling response will determine the applied field.
Alternatively, the vibration control means comprises the vibration control system of the first aspect in combination with a direct shear mode semi-active damping system.
The direct shear mode semi-active damping system may comprise a fluid filled chamber which is acted upon by a piston to vary the characteristics of the fluid. More preferably, the fluid is a magneto-rheological fluid.
Advantageously, the piston is an electromagnet having a variable magnetic field strength. Thus in use, movement of the piston varies the magnetic field strength which in turn influences the alignment of iron particles in the fluid, the aligned particles being sheared as the piston moves.
Advantageously the adaptive vibration control system may be automatic. Alternatively the adaptive vibration control system may operate from a switch.
Preferably also the adaptive vibration control system includes a power supply located adjacent the system. More preferably the power supply is driven from vibration experienced by the structure. The power supply may include piezo material such that movement of the structure creates an electric signal.
Further, the adaptive vibration control system may include a user interface. The user interface may allow a user to provide the signal processor with data on one or more environmental characteristics. The user interface may comprise a wire or wireless connection to a remote device. The remote device may be a handheld device. More preferably, the remote device is a mobile PDA/phone.
According to a fourth aspect of the present invention there is provided a ski, the ski including a vibration control system according to the first aspect to vary stiffness in the ski.
Preferably the vibration control system is arranged fore and aft on the ski body. Advantageously the vibration control system is arranged longitudinally on the ski, on either side of a binding.
According to a fifth aspect of the present invention there is provided a ski, the ski including a vibration control system according to the second aspect to vary damping in the ski.
Preferably the vibration control system is arranged fore and aft on the ski body.
According to a sixth aspect of the present invention there is provided a ski, the ski including a vibration control system according to the first and second aspects to vary both stiffness and damping in the ski.
Preferably the vibration control systems are arranged fore and aft on the ski body. Advantageously the vibration control system according to the first aspect is arranged longitudinally on the ski, on either side of a binding.
According to a seventh aspect of the present invention there is provided a ski, the ski including an adaptive vibration control system according to the third aspect to provide adaptive control of vibration in the ski.
Preferably the sensor arrays are positioned at modal points on the ski. More preferably the sensor arrays are located at a fore and aft location in a body of the ski.
Preferably also the vibration control means are located a modal points on the ski. More preferably the vibration control means are located at fore and aft locations on a body of the ski. Advantageously the vibration control means according to the first aspect is arranged longitudinally on the ski, on either side of a binding.
Preferably the power supply powers the microprocessor and the variable magnetic field. More preferably the power supply comprises a layered piezo-ceramic. The piezo-ceramic may be located on the ski at a position where a skier's boot will rest. Thus the layered piezo-ceramic is configured at the point of maximum weight concentration to ensure it flexes as the skier moves. In this embodiment, power generation comes from the skier's movement over the ski, rather than the vibrating ski.
According to an eighth aspect of the present invention there is provided a chassis for mounting on a ski, the chassis including a vibration control system to control vibration of the ski in use.
By mounting the vibration control system on a chassis, the ski geometry can be varied as required.
Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings in which:
FIGS. 7(a) and 7(b) are illustrations of an adaptive vibration control system mounted on a ski, according to an embodiment of the present invention;
FIGS. 8(a) and (b) are illustrations of a power supply for use on a ski according to an embodiment of the present invention; and
FIGS. 9(a) and (b) are schematic diagrams of a ski chassis, according to an embodiment of the present invention, mounted on a ski.
Reference is initially made to
Between the damping bars 22 and the control rails 26 is located a rheological fluid 28. Rheological fluids are well known and operate by increasing the viscosity of the fluid in response to an applied field. In the embodiment shown the fluid 28 is a magnetorheological fluid which undergoes a change in viscosity in response to a changing magnetic field. This arrangement of bars 22, rails 26 and fluid 28 provides a vibration control system in the form of an active flex control which can vary stiffness in the ski 10.
A first embodiment of the flex control system is illustrated with the aid of
In the preferred embodiment small volumes of fluid 28 are used which require small field strengths so that the ski 10 can be both lightweight and cheap to produce.
An alternative embodiment of the active flex control is shown in
As the ski 10, 62 can vary its stiffness as described hereinbefore, conventional passive-damping techniques would be insufficient as the damping requirements will need to vary. Ski 10 incorporates a semi-active damping system, best illustrated in
Reference is now made to
Like the active flex control, the semi-active damping system can be constructed using small amounts of fluid 28 placed in fibres to reduce weight and cost of the ski 10.
A further embodiment of a semi-active damping system is shown in
Reference is now made to
It will be appreciated by those skilled in the art that the active flex systems and the semi-active damping systems described hereinbefore can be used independently on a ski.
Reference is now made to
Signals from the sensors in the array 36 are input to a signal processing unit 38 which, using a stored algorithm, identifies a characteristic vibration pattern dependent on the environmental conditions and the handling of the ski 10. Unit 38 then determines a response proportional to the amplitude of the vibration which is transmitted to the coils 30 controlling the magnetic field strength. Thus the stiffness and damping can be controlled as described hereinbefore. A feedback loop 40 is also provided to enable the amount of actuator response to be regulated.
Reference is now made to
Further on the ski 100 are arranged arrays of vibration sensors 140a-e. These sensors 140a-e are PVDF piezo-sensors which convert vibrational movement to an electrical signal indicative of the amount of vibration experienced. These sensors 140a-e are positioned at positions, or modal points, where significant vibration is experienced by the ski 100. Thus they are located fore and aft on the ski towards each side.
Located centrally on the ski 100, at the position of the binding is an intelligent control unit 150. Control unit 150 is an advanced version of the adaptive control unit illustrated in
Also included with the intelligent control unit 150 is a control panel 152 which allows a user to input values representative of environmental characteristics into the microprocessor 152. For instance these may be the skiers weight, style, ability and snow condition. The control panel 152 may also include a main switch to enable and disable the unit 150. It will be understood that the control panel 152 may be remote from the unit 150. A cable to a switch located with the skier may, for example, be used. Alternatively the control panel may be a mobile telephone or a PDA (Personal Digital Assistant), providing the user with a wireless connection to the unit 150.
Referring initially to
A further embodiment of the present invention is shown in
The principal advantage of the present invention is that it provides a vibration control system which, when incorporated into a ski, allows control of vibration and improves handling and skier performance by adapting physical properties of the ski.
A further advantage of the present invention is that it allows a single ski to be used for a variety of environmental conditions by varying the stiffness of the ski.
A yet further advantage of the present invention is that it provides a simple pump for semi-active damping control through use of a fluid filled flexed hose.
It will be appreciated by those skilled in the art that various modifications may be made to the invention hereindescribed without departing from the scope thereof. For example, while the embodiment shown is a ski, any object subjected to vibration over a wide bandwidth could be fitted with the vibration control system of the present invention. Additionally, the number of damping bars and shear-mode interfaces could be varied on an object.
Claims
1-39. (canceled)
40. A vibration control system, the system comprising a mounting surface upon which is located a flexible hose, the hose having a first cross-sectional area filled with a rheological fluid and ends abutted to the surface.
41. A vibration control system as claimed in claim 40, wherein the rheological fluid is an electrorheological fluid which undergoes a change in viscosity proportional to a change in electric field.
42. A vibration control system as claimed in claim 40, wherein the rheological fluid is a magnetorheological fluid which undergoes a change in viscosity proportional to a change in applied magnetic field.
43. A vibration control system as claimed in claim 40, wherein a plurality of hoses are located on the surface.
44. A vibration control system as claimed in claim 43, wherein the hoses are located symmetrically on the surface.
45. An adaptive vibration control system, the system comprising sensing means to determine one or more environmental characteristics, a signal processor to determine a controlling response to the characteristics and vibration control means responsive to the controlling response to counter vibration.
46. An adaptive vibration control system as claimed in claim 45, wherein the vibration control means comprises a structure including a chamber and a means for creating a variable applied field within the chamber, wherein the chamber is substantially filled with a theological fluid which under the influence of the applied field causes a variation in the stiffness of the structure.
47. An adaptive vibration control system as claimed in claim 45, wherein the vibration control means comprises a mounting surface upon which is located a flexible hose, the hose having a first cross-sectional area filled with a rheological fluid and ends abutted to the surface.
48. An adaptive vibration control system as claimed in claim 45, wherein the sensing means is at least one sensor.
49. An adaptive vibration control system as claimed in claim 45, wherein the sensing means is a multi-sensor array.
50. An adaptive vibration control system as claimed in claim 45, wherein the multi-sensor array is a distributed array of PVDF piezo-sensors.
51. An adaptive vibration control system as claimed in claim 45, wherein the adaptive vibration control system includes a power supply located adjacent the system, the power supply including a piezo material such that movement of the material creates an electric signal.
52. A ski, the ski including a vibration control system, the system comprising sensing means to determine one or more environmental characteristics, a signal processor to determine a controlling response to the characteristics and vibration control means responsive to the controlling response to counter vibration.
53. A ski as claimed in claim 52, wherein the vibration control means comprises a structure including a chamber and a means for creating a variable applied field within the chamber, wherein the chamber is substantially filled with a theological fluid which under the influence of the applied field causes a variation in the stiffness of the ski.
54. A ski as claimed in claim 52, wherein the vibration control means comprises a mounting surface upon which is located a flexible hose, the hose having a first cross-sectional area filled with a theological fluid and ends abutted to the surface.
55. A ski as claimed in claim 52, wherein the vibration control system comprises vibration control means comprising a structure including a chamber and a means for creating a variable applied field within the chamber, wherein the chamber is substantially filled with a theological fluid which under the influence of the applied field causes a variation in the stiffness of the ski, and vibration control means comprising a mounting surface upon which is located a flexible hose, the hose having a first cross-sectional area filled with a theological fluid and ends abutted to the surface to vary damping of the ski.
56. A ski as claimed in claim 52, wherein the sensing means is a multi-sensor array being a distributed array of PVDF piezo-sensors.
57. A ski as claimed in claim 52, wherein the sensing means is sensor arrays positioned at modal points on the ski.
58. A ski as claimed in claim 52, wherein the vibration control means are located a modal points on the ski.
59. A ski as claimed in claim 52, further comprising a power supply comprising a layered piezo-ceramic, and wherein power generation comes from a skier's movement over the ski acting on the piezo-ceramic.
Type: Application
Filed: Dec 10, 2002
Publication Date: Jul 14, 2005
Inventor: Peter Watson (Richmond N.Yorkshire)
Application Number: 10/498,251