Device and Method for Decreasing Energy Consumption of a Person by Use of a Lower Extremity Exoskeleton
A lower extremity exoskeleton, configurable to be coupled to a person, includes: leg supports configurable to be coupled to the person's lower limbs and designed to rest on the ground during stance phases, with each leg support having a thigh link and a shank link; two knee joints, each configured to allow flexion and extension between respective shank and thigh links; an exoskeleton trunk configurable to be coupled to the person's upper body, rotatably connectable to the thigh links of the leg supports, allowing for the flexion and extension between the leg supports and the exoskeleton trunk; two hip actuators configured to create torques between the exoskeleton trunk and the leg supports; and at least one power unit capable of providing power to the hip actuators. In use, power is supplied to the hip actuators in an amount to reduce the energy consumed by a user during a walking cycle.
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This application represents a continuation of pending U.S. patent application Ser. No. 12/468,595, filed May 19, 2009 which claims the benefit of U.S. Provisional Application No. 61/071,823 entitled DEVICE AND METHOD FOR DECREASING ENERGY CONSUMPTION OF A PERSON BY USE OF A LOWER EXTREMITY EXOSKELETON, filed May 20, 2008.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates generally to the field of lower extremity exoskeletons and, more particularly, to the field of lower extremity exoskeletons that decrease their wearer's energy consumption.
2. Discussion of the Prior Art
In a wide variety of situations, people of ordinary ability often consume a great deal of energy when walking or carrying a load. One attempt to improve load carrying ability is set forth in the paper entitled “A QUASI-PASSIVE LEG EXOSKELETON FOR LOAD-CARRYING AUGMENTATION”, C. J. Walsh, K. Endo, and H. Herr, International Journal of Humanoid Robotics, 2007. However, the quasi-passive exoskeleton taught by Walsh et al. increases its wearer's oxygen consumption. More specifically, the exoskeleton described has no actuation and power unit and therefore will not be able to transfer power from the exoskeleton to the person. This means that this type of system, regardless of the location and strength of its springs, will not decrease its wearer's energy expenditure. Since oxygen consumption is proportional to energy expended, a wearer's oxygen consumption will not be decreased.
An article published by Popular Science Magazine (May 2008) describes a powered exoskeleton system designed and built by Sarcos, that is controlled by a method called “get out of the way”. This method measures the forces and torques a wearer exerts onto the exoskeleton and drives the exoskeleton based on these measurements. This “get out of the way” control method has been extensively used in control of intelligent assist devices. See U.S. Pat. Nos. 6,299,139, 6,386,513, and 6,886,812. However, the “get out of the way” control method will not reduce a wearer's energy expenditure because the force from the exoskeleton onto the wearer is in the opposite direction to the wearer's motion and in fact increases the wearer's energy expenditure.
Based on the above, opportunities exist to provide a general purpose exoskeleton device that will decrease the wearer's energy consumption while the device is worn. Providing an exoskeleton that decreases the energy consumption of its wearer would allow a wearer to walk and carry heavy objects, while reducing the wearer's energy expenditure. In particular, this invention covers various embodiments of exoskeleton devices that decrease their wearers' energy expenditure during a stance phase.
SUMMARY OF THE INVENTIONThe opportunities described above are addressed in several embodiments of a lower extremity exoskeleton, wearable by a person. The lower extremity exoskeleton described here is configurable to be coupled to a person and, among other components, comprises: two leg supports configurable to be coupled to the person's lower limbs; two knee joints, each of which is configured to allow flexion and extension between a respective shank link and respective thigh link; an exoskeleton trunk, which is configurable to be coupled to the person's upper body and is rotatably connectable to the thigh links of the leg supports, allowing for the flexion and extension between the leg supports and the exoskeleton trunk; two hip actuators, which are configured to create torques between the exoskeleton trunk and leg supports; and at least one power unit, which is capable of providing power to the hip actuators, among other components. In operation, when the lower extremity exoskeleton is worn by the person, one leg support is in the stance phase and the other leg support is in the swing phase, the power unit is configured to cause the hip actuator of the leg support in the stance phase to create a torque profile such that the energy supplied by the power unit to the hip actuator of the leg support in stance phase is greater than the energy required to move the exoskeleton trunk and the leg support in stance phase through the same trajectory when not worn by the person.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein:
In accordance with an embodiment of the present invention,
Lower extremity exoskeleton 100, among other things, further comprises two hip actuators 145 and 146 which are configured to create torques between exoskeleton trunk 109 and leg supports 101 and 102. Right hip actuator 145 is shown in
In operation, when right leg support 101 is in the stance phase and left leg support 102 is in the swing phase, power unit 201 is configured to cause the corresponding right hip actuator 145 of right leg support 101 to create a torque profile. Because of this torque profile, lower extremity exoskeleton 100 and person 187 travel from configuration A to configuration C (as shown in
In summary:
If WACTUATOR>(EC−EA+ELOSS), energy transferred to person 187=WACTUATOR−(EC−EA+ELOSS)
If WACTUATOR<(EC−EA+ELOSS), energy transferred from person 187=(EC−EA+ELOSS)−WACTUATOR
The required energy to move exoskeleton trunk 109 and right leg support 101 through the same trajectory from A to C when exoskeleton 100 is not worn by person 187 is (EC−EA+ELOSS). This means that, to transfer energy to person 187 during the stance phase of right leg support 101, the energy supplied by power unit 201 to right hip actuator 145 of right leg support 101 must be larger than the energy required to move exoskeleton trunk 109 and right leg support 101 through the same trajectory from A to C when person 187 is not present. An incremental increase in mechanical energy transferred to person 187 during the stance phase will result in an incremental decrease in wearer's energy required for locomotion during the stance phase. Since the wearer's oxygen consumption is proportional with the energy expenditure, a decrease in the wearer's energy required for locomotion leads to less oxygen consumption by the wearer. One way to ensure mechanical energy is transferred to person 187 during the stance phase is to ensure that the torque profile of right hip actuator 145 of right leg support 101 is generally larger than the torque required to move exoskeleton trunk 109 and right leg support 101 through the same trajectory from A to C when person 187 is not present. This is described below with the help of
The Kinetic energy and the Potential energy of the system shown in
where:
- MTRUNK: mass of exoskeleton trunk 109 and any attached load (e.g., rear load 118)
- ML: mass of right leg support 101
- I: moment of inertia of right leg support 101 about point F
- L: length of right leg support 101 during stance as shown in
FIG. 5 - R: distance between the center of mass of right leg support 101 and point F (not shown in any figure)
- β1: the angle between ground 130 and a line normal to a line between points E and F (angle between force FE1 and ground 130)
- β2: the angle between ground 130 and a line normal to exoskeleton trunk 109 (angle between force FE2 and ground 130)
- α: ground slope (angle between ground 130 and horizontal ground 134)
- D distance between force FE2 and point F
- K A constant quantity
Writing a dynamic equation for the exoskeleton shown in
TE=(MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF+FE1L Cos(β2−β1)+FE2D (3)
where:
- FE1 force on exoskeleton trunk 109 from Person's upper body 149, assumed to be normal to the exoskeleton trunk 109 (positive value is shown in
FIG. 5 ) - FE2 force on right leg support 101 from person right lower limb 143, assumed to be normal to a line between points E and F (positive value is shown in
FIG. 5 ) - TE: torque generated by right hip actuator 145 (positive value decreases angle λ)
- TF: friction torque opposing the motion of right leg support 101 relative to exoskeleton trunk 109
Since β2 is relatively constant in comparison to angle λ (exoskeleton trunk 109 does not rotate much) any interaction torque between person's upper body 149 and exoskeleton trunk 109 will not appear in equation (3). Only the interaction force (e.g., FE1 from person' upper body 149 onto exoskeleton trunk 109) affects the motion of exoskeleton trunk 109.
Rearranging the terms in equation (3) results in equation (4):
FE1L Cos(β2−β1)+FE2D=TE−(MTRUNKL2+I){umlaut over (β)}1+(LMTRUNK+RML)g Sin(β1+α)−TF (4)
Assume for a moment that FE2=0. This assumption is only for the sake of understanding the conditions under which the wearer's energy expenditure is reduced. Later, this assumption will be removed. If FE2=0, equation (4) reduces to equation (5).
We will consider three cases described below.
Case 1As can be examined from equation (5), if the hip actuator torque TE is such that:
TE>(MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF (6)
Then FE1>0. This means if the hip actuator torque is chosen such that it is larger than the addition of the inertial torque (MTRUNKL2+I){umlaut over (β)}1, gravitational torque, −(L MTRUNK+R ML)g Sin(β1+α), and the frictional torque TF, then the force from person 187 on exoskeleton trunk 109 FE1 is positive. This means the force from person 187 on exoskeleton trunk 109 is in the direction shown in
The situation of Case 1 (described above) shows that in order to reduce the wearer's energy expenditure while walking (and consequently oxygen consumption and heart rate), the torque profile from the hip actuator, when exoskeleton 100 is worn by person 187, should create a force from exoskeleton trunk 109 onto person's upper body along the person's forward velocity direction 162. This means that to reduce the wearer's energy expenditure while walking, person 187 should be pushed forwardly by exoskeleton trunk 109. The above Case 1 also indicates that to reduce the wearer's energy expenditure while walking (and consequently oxygen consumption and heart rate), the torque profile from the hip actuator, when exoskeleton 100 is worn by person 187, should be larger than the torque required to move exoskeleton trunk 109 and leg support 101 during stance phase through the same trajectory when not worn by person 187.
Case 2As can be examined from equation (5), if the hip actuator torque, TE, is such that:
TE<(MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF (7)
then FE1<0. This means that if the hip actuator torque is chosen so that it is smaller than the addition of the inertial torque (MTRUNKL2++I){umlaut over (β)}1, gravitational torque, −(LMTRUNK+RML)g Sin(β1+α) and the frictional torque TF, then the force on the exoskeleton, FE1, is negative. This means the force from person 187 on exoskeleton trunk 109 is in the opposite direction shown in
If TE=(MTRUNKL2+I){umlaut over (β)}1−(LLMTRUNK+DML)g Sin(β1+α)+TF (8)
Then FE1=0. This means if the hip actuator torque is chosen to be exactly equal to the summation of the inertial torque (MTRUNKLL2+I){umlaut over (β)}1, gravitational torque, −(LLMTRUNK+RML)g Sin(β1+α), and the frictional torque TF, then the interaction force between person 187 and the exoskeleton, FE is zero. This means the person does not feel the exoskeleton and therefore the power person 187 is spending is the same as what he/she would be spending when walking without any exoskeleton. This means no energy is transferred between the exoskeleton and its wearer. In this case, the wearer's energy expenditure neither increases nor decreases.
If FE2≠0, the left side of equation (9) represents the torque from person 187 onto lower extremity exoskeleton 100 about point F:
FE1L Cos(β2−β1)+FE2D=TE−(MTRUNKL2+I){umlaut over (β)}1+(LMTRUNK+RML)g Sin(β1+α)−TF (9)
The three cases described previously for equation (5) can be repeated for equation (9) as described below.
Case 1As can be examined from equation (9) if hip actuator torque TE is such that:
TE>(MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF (10)
Then FE1 L Cos(β2−β1)+FE2 D>0. This means if the actuator torque is chosen such that it is larger than the summation of the inertial torque (MTRUNKL2+I){umlaut over (β)}1, gravitational torque −(L MTRUNK+R ML)g Sin(β1+α), and the frictional torque TF, then the torque from person 187 onto lower extremity exoskeleton 100 about point F, FE1 L Cos(β2−β1)+FE2 D, is positive. This means that the torque from person 187 on lower extremity exoskeleton 100 is in the counterclockwise direction and the torque on person 187 is in the clockwise direction and along the person's forward velocity direction 162. When the torque on person 187 is along the person's forward velocity direction 162 (as shown in
The situation of Case 1 (described above) teaches that to reduce the wearer's energy expenditure while walking (and consequently oxygen consumption and heart rate), the torque profile from hip actuator when exoskeleton 100 is worn by person 187 should create a clockwise torque from exoskeleton 100 onto person 187 about point F. This means that to reduce the wearer's walking energy expenditure, person 187 should be pushed forwardly by exoskeleton 100. The above Case 1 also teaches that to reduce the wearer's energy expenditure while walking (and consequently oxygen consumption and heart rate), the torque profile from hip actuator when exoskeleton 100 is worn by person 187 should be larger than the torque required to move exoskeleton trunk 109 and leg support in stance phase through the same trajectory when not worn by person 187.
Case 2As can be examined from equation (9) if the hip actuator torque, TE is such that:
TE<(MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF (11)
Then FE1 L Cos(β2−β1)+FE2 D<0. This means that if the hip actuator torque is chosen such that it is smaller than the summation of the inertial torque (MTRUNKL2+I){umlaut over (β)}1, gravitational torque −(L MTRUNK+R ML)g Sin(β1+α), and the frictional torque TF, then the torque from person 187 onto lower extremity exoskeleton 100 about point F, FE1 L Cos(β2−β1)+FE2 D, is negative. This means that the torque from person 187 on lower extremity exoskeleton 100 about point F is in the clockwise direction and the torque on person 187 is opposite to the person's forward velocity direction 162 (counterclockwise direction). When the torque on person 187 is opposite to the person's forward velocity direction 162 (as shown in
As can be examined from equation (9), if the hip actuator torque TE is such that:
TE(MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF (12)
Then FE1 L Cos(β2−β1)+FE2 D=0. This means the torque from person 187 onto lower extremity exoskeleton 100 about point F is zero. If the time integral of this power over the entire stance time is zero, no mechanical energy is transferred between lower extremity exoskeleton 100 and person 187. In this case, the wearer's energy expenditure neither increases nor decreases.
Remark 1Since exoskeleton trunk 109 rotates very little (i.e., β2 is relatively constant in comparison to angle λ) and the summation of torques on exoskeleton trunk 109 is zero, equation (13) states that the torque on exoskeleton trunk 109 from person's upper body cancels the algebraic summation of the reaction torques from hip actuators 145 and 146.
TP=TE−TS−TG (13)
where:
- TP: Torque on exoskeleton trunk 109 from person's upper body 149
- TE: Torque on exoskeleton trunk 109 from the leg support in stance phase
- TS: Torque on exoskeleton trunk 109 from the leg support in swing phase (TS is positive when it tries to turn the exoskeleton trunk in the CW direction around point E
- TG: Torque due to the weight of the exoskeleton trunk and any attached load around point E (TF is positive when it tries to turn the exoskeleton trunk in the CW direction around point E)
If the leg support that is in the swing phase swings by force of the person, TS is zero. If the leg support that is in the swing phase swings by power of the hip actuator, TS is not zero. To reduce TP (the torque on exoskeleton trunk 109 from person's upper body 149), equation (13) suggests that the leg support in the swing phase be powered (i.e., TS should be nonzero). This means the hip actuator of the swinging leg should impose a torque in the opposite direction of the hip torque in the stance phase, to reduce the torque the person's upper body 149 supports.
Remark 2In general, any lower extremity exoskeleton, regardless of the number of actuators and their locations on the exoskeleton system, decreases its wearer's energy expenditure as long as the force from the exoskeleton trunk onto the wearer's upper body is along the person's forward velocity. For example one can install at least one actuator on each exoskeleton ankle and provide a force from the exoskeleton trunk onto the wearer's upper body along the person's forward velocity. When the force on the person is in the direction along the person's forward velocity, regardless of the exoskeleton architecture, mechanical power is transferred from the exoskeleton to the person. Mechanical energy transferred to the person during the stance phase, will result in an incremental decrease in wearer's energy required for locomotion. An incremental decrease in wearer's energy required for locomotion leads to less oxygen consumption and lower heart rate.
Remark 3The above analysis shows how a lower extremity exoskeleton can reduce its wearer's energy expenditure during the stance phase. An exoskeleton system that has two arms, in addition to two lower extremities, can also reduce its wearer's energy expenditure as long as the lower extremities of the exoskeleton function according to the teaching described above.
In some embodiments, hip actuators 145 and 146 each comprise a hydraulic hip actuator. In these embodiments, at least one power unit 201 provides hydraulic power to hip actuators 145 and 146. In some embodiments, only one power unit 201 provides hydraulic power to hydraulic hip actuators 145 and 146. In some embodiments, each hydraulic hip actuator receives hydraulic power from separate power units. In some embodiments, power unit 201, as shown in
By controlling electric motor 241, a torque profile can be implemented on hip actuators 145, 146 to satisfy the inequalities (6) or (10). Since the torque is a function of the hydraulic pressure and the hip actuator geometry, the hip actuator torque can be controlled by creating a closed loop control on the electric motor 241 by measuring the hydraulic pressure as the feedback variable. In some embodiments, the hip actuator torque can be controlled to satisfy inequalities (6) or (10) by creating a closed loop control on the electric motor 241 by measuring the hip actuator torque or force as the feedback variable.
In some embodiments, as shown in
In some embodiments, as shown in
Hydraulic hip actuators 145 and 146 comprise any hydraulic actuators or combination of actuators capable of converting pressurized hydraulic fluid into force or torque. Examples of hydraulic actuators include, without limitation, linear hydraulic piston-cylinders, rotary hydraulic actuators, rack-and-pinion-type rotary actuators and rotary hydraulic vane type actuators where pressurized hydraulic fluid, by pushing against moving surfaces, generate force or torque.
Actuated flow restricting valve 200 comprises any valve or combination of valves capable of performing the indicated functions. Examples of actuated flow restricting valve 200 include, without limitation, flow control valve, pressure control valve, actuated needle valves, solenoid valves and on-off valves. Hydraulic pump 240 comprises any pump or combination of pumps capable of performing the indicated functions. Examples of hydraulic pump 240 include, without limitation gear pump, vane pump, axial piston pump, and radial piston pump.
Electric motor 241 comprises any device or combination of devices capable of driving hydraulic pump 240. Examples of motor 241 include, without limitation, electric motors, including, without limitation, AC (alternating current) motors, brush-type DC (direct current) motors, brushless DC motors, electronically commutated motors (ECMs), stepping motors, and any combination thereof. Although we state that electric motor 241 turns hydraulic pump 240, one skilled in the field can realize that both motor 241 and hydraulic pump 240 may have other types of non-rotational couplings, such as reciprocating linear motion.
In some embodiments of the invention, lower extremity exoskeleton 100 comprises at least one signal processor 159 capable of controlling hip actuators 145 and 146. Signal processor 159 comprises an element or combination of elements selected from a group consisting of analog devices; analog computation modules; digital devices including, without limitation, small-, medium-, and large-scale integrated circuits, application specific integrated circuits, programmable gate arrays, programmable logic arrays; electromechanical relays, solid state switches, MOSFET switches and digital computation modules including, without limitation, microcomputers, microprocessors, microcontrollers, and programmable logic controllers. In operation, to decrease the wearer's energy expenditure, signal processor 159 computes a torque profile that satisfies inequalities (6) or (10). This torque is then produced by hip actuators 145 and 146 during their respective stance phase.
In some embodiments where hip actuators 145 and 146 are hydraulic actuators, signal processor 159, by controlling electric motor 241, computes a torque profile as described in inequalities (6) or (10) for hip actuators 145 and 146. Since the torque is a function of the hydraulic pressure and the hip actuator geometry, the hip actuator torque in some embodiments, as shown in
Signal processor 159, in some embodiments, is mounted to exoskeleton trunk 109. In some embodiments, signal processor 159 is located inside power unit 201. Signal processor 159 may be a simple mechanical device consisting of a hydraulic or pneumatic circuit, or it may include electronic elements as well.
In some embodiments, as shown in
Further discussing the geometry of the exoskeleton shown in
In some embodiments, exoskeleton trunk 109 is configured to hold a rear load 118 behind person 187.
Some embodiments, as shown in
In accordance with another embodiment of the invention,
In accordance with another embodiment of the invention,
In some embodiments, as shown in
In some embodiments, as shown in
In accordance with another embodiment,
In some embodiments, as shown in
In some embodiments, as shown in
In some embodiments, as shown in
Also, in some embodiments, as shown in
In some embodiments, as shown in
In some embodiments, as shown in
In some embodiments, exoskeleton feet 139 and 140 rotate about two plantar-dorsi flexion axes relative to shank links 105 and 106.
In some embodiments, exoskeleton feet 139 and 140 rotate about two ankle abduction-adduction axes relative to shank links 105 and 106.
In some embodiments, exoskeleton feet 139 and 140 rotate about an ankle rotation axes 147 relative to shank links 105 and 106. In some embodiments, as shown in
In some embodiments, as shown in
Also shown in
In some embodiments, lower extremity exoskeleton 100 (as shown in
In some embodiments, as shown in
In some embodiments, torque generators 110 and 111 are friction brakes where one can control the resistive torque on knee joints 107 and 108 by controlling the friction torques. In other embodiments, torque generators 110 and 111 are viscosity based friction brakes where one can control the resistive torque on knee joints 107 and 108 by controlling the viscosity of the fluid. In other embodiments, torque generators 110 and 111 are Magnetorheological Fluid Devices where one can control the resistive torque on knee joints 107 and 108 by controlling the viscosity of the Magnetorheological Fluid. One skilled in the art realizes that any of the above devices can be mounted in the invention to function in the same way as the hydraulic rotary dampers shown in
In some embodiments, signal processor 159 is configured to control torque generators 110 and 111. Signal processor 159 controls the resistance to flexion in knee joints 107 and 108 as a function of stance signals 219 and 220. For example, when right stance sensor 160 detects the stance phase in right leg support 101, signal processor 159 will increase the impedance of right torque generator 110 so that right knee joint 107 resists flexion. Conversely, when right stance sensor 160 detects the swing phase in right leg support 101, signal processor 159 will decrease the impedance of right torque generator 110 so that no resistance to flexion occurs in right knee joint 107. Similarly, when stance sensor 161 detects the stance phase in left leg support 102, signal processor 159 will increase the impedance of left torque generator 111 so that left knee joint 108 resists flexion. Conversely, when left stance sensor 161 detects the swing phase in left leg support 102, signal processor 159 will decrease the impedance of left torque generator 111 so that no resistance to flexion occurs in left knee joint 108. Large impedances of torque generators 110 and 111 lead to large resistance of knee joints 107 and 108 to flexion needed during stance phase. Conversely, small impedances of torque generators 110 and 111 lead to small resistance of knee joints 107 and 108 to flexion needed during swing phase. In some embodiments, signal processor 159 is mounted to torque generators 110 and 111.
In practice, the resistance to flexion in knee joints 107 and 108 during the stance phase need not be constant. In some embodiments, the resistance to flexion at the beginning of the stance phase (approximately the first 20% of the stance cycle) may be extremely high (i.e., knee joints 107 and 108 will be locked in the beginning of stance). During the middle of the stance phase (approximately the 20% to 80% of the stance cycle), the resistance to flexion may be lower, but high enough that knee joints 107 and 108 will only undergo a few degrees of flexion. During the end of the stance cycle (approximately the last 20% of the stance cycle), the resistance to flexion may be low, but still nonzero, so that knee joint 107 and 108 may flex in preparation for the swing cycle.
In some embodiments, each of leg supports 101 and 102 further comprises a torque generator wherein each torque generator comprises a hydraulic piston-cylinder. In these embodiments, power unit 201, among other components, comprises at least one knee hydraulic circuit 190 connectable to torque generators 110 and 111. Knee hydraulic circuit 190 is configured to modulate the fluid flow to torque generators 110 and 111. In operation (using right leg support 101 as an example), when right leg support 101 is in a stance phase, knee hydraulic circuit 190 is configured to restrict the fluid flow to right torque generator 110 of right leg support 101. Knee hydraulic circuit 190, when leg support 101 is in a swing phase, is configured to allow the fluid flow to right torque generator 110 of right leg support 101. In other words, knee hydraulic circuit 190, when leg support 101 is in a stance phase, is configured to increase the resistance to flexion of right knee joint 107. Knee hydraulic circuit 190, when leg support 101 is in a swing phase, is configured to decrease the resistance to flexion of right knee joint 107. The above behavior is also true for leg support 102. In some embodiments of the invention, lower extremity exoskeleton 100 further comprises at least one stance sensor 160 and 161 for each of leg supports 101 and 102. Stance sensors 160 and 161 produce stance signals 219 and 220, indicating whether leg supports 101 and 102 are in the stance phase. In some embodiments, knee hydraulic circuit 190 and hydraulic circuit 194 may be coupled to each other or share components. In some embodiments, one knee hydraulic circuit 190 may be used for both torque generator 110 and 111, or each of torque generators 110 and 111 may connect to an independent knee hydraulic circuit 190.
In some embodiments, leg supports 101 and 102 are configured to allow flexion of the respective knee joints 107 and 108 during the swing phase and to resist flexion of the respective knee joints 107 and 108 during the stance phase by locking the knees. One such locking knee is shown in
In some embodiments, lower extremity exoskeleton 100 further comprises knee resilient elements 232, which are configured to encourage flexion of knee joints 107 and 108. This decreases the person's effort needed to flex knee joints 107 and 108 during the swing phase. In some embodiments, as shown in
Although various exemplary embodiments have been described, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the described device as specifically shown here without departing from the spirit or scope of that broader disclosure. For example, in general, the exoskeleton legs do not have to reach all the way to the ground in order to decrease the wearer's oxygen consumption. Any leg support including shank links only, as shown in
Claims
1. A method of reducing energy consumption of a person in motion along a trajectory in a forward direction of movement coupled to an exoskeleton device including at least one power unit, two leg supports for coupling to said person's lower limbs rotatably connected to an exoskeleton trunk, and two hip actuators for creating torques between said leg supports and said exoskeleton trunk, said method comprising: supplying energy from said at least one power unit to said hip actuator of the leg support coupled to said person's lower limb in a stance phase wherein said energy is determined based on a force between said exoskeleton trunk and the person's upper body along the person's forward velocity direction and established to be larger than an amount of energy required to move said exoskeleton trunk and said leg support in the stance phase through the same trajectory in the forward direction of movement when not worn by said person.
2. The method of claim 1, further comprising: determining said energy to establish a torque profile for controlling said hip actuator of said leg support in the stance phase to ensure said torque profile is larger than:
- (MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF
- wherein: MTRUNK is a mass of the exoskeleton trunk and any attached load; ML is a mass of the respective first and second leg support in the stance phase; I is moment of inertia of the respective first and second leg support in the stance phase; L is a length of the respective first and second leg support in the stance phase; R is a distance between a center of mass of the respective first and second leg support in the stance phase and a rotational point; g is force due to gravity; β1 is an angle between a support surface and the normal line of force on the exoskeleton trunk from the person's upper body; α is a ground slope defined by an angle between a support surface and a horizontal plane; and TF is a frictional torque opposing the motion of the leg support relative to the exoskeleton trunk.
3. The method of claim 1, wherein supplying energy from said at least one power unit to said hip actuator of the leg support coupled to said person's lower limb in the stance phase includes creating a torque profile in said hip actuator of said leg support in the stance to provide torque at least equal to an amount of torque required to move said exoskeleton trunk and said leg support in the stance phase through the same trajectory in the forward direction of movement when not worn by said person.
4. The method of claim 3, wherein each said leg support further comprises a thigh link, a shank link, and a knee joint configured to allow flexion and extension between said shank link and said thigh link, said method further comprising: allowing flexion and extension of a respective said knee joint during a swing phase and resisting flexion of the respective said knee joint during the stance phase to allow a transfer of force to the ground.
5. The method of claim 1, wherein supplying energy from said at least one power unit to said hip actuator of the leg support coupled to said person's lower limb in the stance phase includes creating a force from said exoskeleton trunk onto the person's upper body by use of said hip actuator of said leg support in the stance phase, wherein said force from said exoskeleton trunk onto the person's upper body is along the person's forward velocity.
6. The method of claim 5 further comprising:
- measuring the force between said exoskeleton trunk and the person's upper body; and
- ensuring that the force from said exoskeleton trunk onto the person's upper body is always along the person's forward velocity.
7. The method of claim 1, further comprising: transferring weight of a load to said exoskeleton trunk through a connecting bracket.
8. The method of claim 7, further comprising: holding the load in front of the person through an extension frame when said exoskeleton trunk is coupled to said person's upper body.
9. The method of claim 1, further comprising: producing a stance signal utilizing at least one stance sensor for each said leg support, with the stance signal indicating whether a respective said leg support is in the stance phase.
10. The method of claim 9, wherein said at least one stance sensor is located inside or connected to a bottom of a human shoe.
11. The method of claim 1, wherein each said leg support includes a foot configured to rest on the ground and each said foot includes at least one stance sensor, said method further comprising: producing a stance signal utilizing the at least one stance sensor indicating whether a respective said leg support is in the stance phase.
12. A method of reducing energy consumption of a person in motion along a trajectory in a forward direction of movement coupled to an exoskeleton device including at least one power unit, two leg supports rotatably connected to an exoskeleton trunk for attachment to the person's legs, and two hip actuators for creating torques between said leg supports and said exoskeleton trunk, the method comprising: supplying energy from said at least one power unit to said hip actuator of the leg support coupled to said person's lower limb in a stance phase to create a force from said exoskeleton trunk onto the person's upper body by use of said hip actuator of said leg support in the stance phase, wherein said force from said exoskeleton trunk onto the person's upper body is along the person's forward velocity and larger than an amount of energy required to move said exoskeleton trunk and said leg support in the stance phase through the same trajectory in the forward direction of movement when the exoskeleton is not worn by said person.
13. The method of claim 12, further comprising: measuring a force between said exoskeleton trunk and the person's upper body and ensuring that the force from said exoskeleton trunk onto the person's upper body is always along the person's forward velocity.
14. The method of claim 12, further comprising: transferring weight of a load to said exoskeleton trunk through a connecting bracket.
15. The method of claim 14, further comprising: holding the load in front of the person through an extension frame when said exoskeleton trunk is coupled to said person's upper body.
16. The method of claim 12, further comprising: producing a stance signal utilizing at least one stance sensor for each said leg support, with the stance signal indicating whether a respective said leg support is in the stance phase.
17. The method of claim 16, wherein each said leg support includes a foot configured to rest on the ground, and each said foot includes the at least one stance sensor producing the stance signal.
18. The method of claim 12, further comprising: determining said energy to establish a torque profile for controlling said hip actuator of said leg support in the stance phase to ensure said torque profile is larger than:
- (MTRUNKL2+I){umlaut over (β)}1−(LMTRUNK+RML)g Sin(β1+α)+TF
- wherein: MTRUNK is a mass of the exoskeleton trunk and any attached load; ML is a mass of the respective first and second leg support in the stance phase; I is moment of inertia of the respective first and second leg support in the stance phase; L is a length of the respective first and second leg support in the stance phase; R is a distance between a center of mass of the respective first and second leg support in the stance phase and a rotational point; g is force due to gravity; β1 is an angle between a support surface and the normal line of force on the exoskeleton trunk from the person's upper body; α is a ground slope defined by an angle between a support surface and a horizontal plane; and TF is a frictional torque opposing the motion of the leg support relative to the exoskeleton trunk.
19. The method of claim 12, wherein supplying energy from said at least one power unit to said hip actuator of the leg support coupled to said person's lower limb in the stance phase includes creating a torque profile in said hip actuator of said leg support in the stance to provide torque at least equal to an amount of torque required to move said exoskeleton trunk and said leg support in the stance phase through the same trajectory in the forward direction of movement when not worn by said person.
20. The method of claim 19, wherein each said leg support further comprises a thigh link, a shank link, and a knee joint configured to allow flexion and extension between said shank link and said thigh link, said method further comprising: allowing flexion and extension of a respective said knee joint during a swing phase and resisting flexion of the respective said knee joint during the stance phase to allow a transfer of force to the ground.
21. A method of reducing the energy consumption of a person in motion along a direction of movement coupled to an exoskeleton device including at least one power unit, two leg supports for coupling to said person's lower limbs rotatably connected to an exoskeleton trunk, two hip actuators for creating torques between said leg supports and said exoskeleton trunk, and at least one signal processor, said method comprising:
- supplying energy from said at least one power unit to said hip actuator of the leg support coupled to said person's lower limb in a stance phase and creating a torque profile for said hip actuator of said leg support in the stance phase such that mechanical energy is transferred to said person from said lower extremity exoskeleton during said stance phase in the direction of movement, wherein said signal processor computes said torque profile and controls said hip actuator of said leg support in the stance phase to ensure said torque profile is larger than the sum of inertial, gravitation and frictional torques on said leg support in the stance phase.
22. A method of reducing energy consumption of a person in motion along a trajectory in a direction of movement coupled to an exoskeleton device including two leg supports for coupling to said person's lower limbs rotatably connected to an exoskeleton trunk, two hip actuators for creating torques between said leg supports and said exoskeleton trunk, at least one power unit for providing power to said hip actuators, and at least one processor wherein, when said lower extremity exoskeleton is worn by the person, one of the two leg supports is in a stance phase and another of the two leg supports is in a swing phase, said method comprises:
- creating a torque profile which is larger than a required torque or energy needed to move said exoskeleton trunk and said one of the two leg supports in the stance phase through the same trajectory when not worn by said person; and
- causing the hip actuator for said one of the two leg supports which in the stance phase to follow the torque profile.
Type: Application
Filed: Jan 26, 2015
Publication Date: May 14, 2015
Applicant: Ekso Bionics, Inc. (Richmond, CA)
Inventors: Kurt Amundson (Berkeley, CA), Nathan Harding (Oakland, CA), Homayoon Kazerooni (Berkeley, CA)
Application Number: 14/605,343
International Classification: A61H 3/00 (20060101);