High-load leg-foot robot based on hydraulic static support and control method

Abstract

The application discloses a high-load leg-foot robot based on hydraulic static support and a control method, and belongs to the field of leg-foot robots. The robot comprises a lower leg rod, a thigh rod, a thigh parallel rod, a lower leg parallel rod, a lower leg steering rod, a thigh steering rod, a thigh slider connecting rod, a lower leg slider connecting rod, a thigh slider, a lower leg slider and a hydraulic drive unit. The application adopts a structure form of connecting rods plus a hydraulic drive unit, can transfer the load of the leg-foot robot support phase to the hydraulic drive unit, and supports statically by the hydraulic drive unit. Moreover, in the motion state, the hydraulic drive unit does not cause interference to the motion of the leg swing phase. The application can be used for the structural optimization of the existing leg-foot robot, and can effectively improve the load capacity of the leg-foot robot.

Description

Technical Field

[0001] This invention belongs to the field of legged robots and relates to a high-load legged robot based on hydrostatic support and its control method. Background Technology

[0002] Legged robots are an important research area in robotics. Compared to common wheeled robots, legged robots have excellent adaptability to various terrains and can overcome most obstacles in their path. Currently, most legged robots on the market are powered by either electric motors or hydraulic systems.

[0003] For motor-driven legged robots, the motors themselves are lightweight, easy to control, and have a fast response time, so these robots are generally lightweight, small in size, and highly flexible. However, these robots have poor load capacity, with a load-to-weight ratio of only 0.3 to 0.4.

[0004] While hydraulically driven legged robots possess strong load-bearing capacity, their responsiveness and dexterity are relatively poor due to the use of hydraulic actuators for motion control. Furthermore, due to the weight limitations of the hydraulic system itself, these robots are often large in size and weight.

[0005] To overcome the above-mentioned shortcomings, it is necessary to design a legged robot that can both ensure its own flexibility and provide a high load-bearing capacity. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-load legged robot based on hydrostatic support and its control method. This invention can effectively improve the load capacity of current motor-driven legged robots while not affecting the movement of their leg swing phase, thus ensuring their mobility.

[0007] The specific technical solution adopted in this invention is as follows:

[0008] In a first aspect, the present invention provides a high-load legged robot based on hydrostatic support, comprising a left leg and a right leg; the left leg and the right leg have the same structure and each includes a lower leg rod, a thigh rod, a thigh parallel rod, a lower leg parallel rod, a lower leg steering rod, a thigh steering rod, a lower leg slider link, a thigh slider link, a thigh slider, a lower leg slider, and a hydraulic drive unit;

[0009] The upper end of the calf rod is hinged to the lower end of the thigh rod, and the upper end of the thigh rod is hinged to the upper ends of the calf parallel rod and the calf steering rod. The upper ends of the calf parallel rod and the calf steering rod are fixedly connected. The upper end of the thigh rod is fixedly connected to the upper end of the thigh steering rod. The lower end of the thigh parallel rod is hinged to the calf rod, and the upper end is hinged to the lower end of the calf parallel rod. One end of the calf slider connecting rod is hinged to the lower end of the calf steering rod, and the other end is fixed with a calf slider that can slide along the slide rail. One section of the thigh slider connecting rod is hinged to the lower end of the thigh steering rod, and the other end is fixed with a thigh slider that can slide along the slide rail. Along the driving direction, one end of the hydraulic drive unit is fixedly connected to the calf slider, and the other end is fixedly connected to the thigh slider.

[0010] Preferably, the ratio of the length of the lower leg rod and the lower leg steering rod is equal to the ratio of the length of the thigh rod and the thigh steering rod.

[0011] Preferably, the thigh bar, the thigh parallel bar, the calf parallel bar, and the calf bar located above the hinge point with the thigh parallel bar together form a parallelogram.

[0012] Preferably, the sliding axes of the thigh slider and the calf slider coincide, and the upper end of the thigh rod is also located on this axis.

[0013] Preferably, the angle between the thigh rod and the thigh steering rod, and the angle between the lower leg parallel rod and the lower leg steering rod are both...

[0014] Furthermore, the angle between the sliding axes of the thigh slider and the calf slider and the vertical direction is also [value missing].

[0015] Preferably, the lengths of the lower leg steering rod and the lower leg slider connecting rod are equal, and the lengths of the thigh steering rod and the thigh slider connecting rod are equal.

[0016] Preferably, the maximum load of the hydraulic drive unit is greater than or equal to the average maximum load per leg of the robot. The ratio is k, where k is the ratio of the length of the lower leg rod to the length of the lower leg steering rod.

[0017] Preferably, the lower leg rod and the upper leg rod are moved independently by the lower leg rod motor and the upper leg rod motor, respectively; and when the motor is driving the movement, the hydraulic drive unit is unlocked, so that the distance between the upper leg slider and the lower leg slider can be freely changed.

[0018] Secondly, the present invention provides a control method for a high-load legged robot based on hydrostatic support as described in any of the first aspects, as follows:

[0019] S1: When the robot is in the left foot support phase, the right foot is about to be lifted; at this time, the robot controls the left leg hydraulic drive unit to lock, and the robot's left foot cannot move up and down; the robot controls the right leg hydraulic drive unit to unlock; then the robot's right foot is lifted and enters the swinging state, at which time the robot's right foot can move up and down;

[0020] S2: The robot's right leg swings forward; during this process, the hydraulic drive unit of the robot's left leg remains locked, while the hydraulic drive unit of the right leg is always unlocked;

[0021] S3: The robot's right foot touches the ground, entering the double-leg support phase; at this time, the hydraulic drive units of both legs of the robot are locked, and neither leg can move up or down;

[0022] S4: The robot enters the right leg support phase and prepares to lift its left leg; at this time, the robot controls the right leg hydraulic drive unit to lock, and the robot's right leg cannot move up and down; the robot controls the left leg hydraulic drive unit to unlock; then the robot lifts its left leg and enters the swinging motion, at which time the robot's left leg can move up and down.

[0023] S5: The robot's left leg swings forward; during this process, the robot's right leg hydraulic drive unit remains locked, while the left leg hydraulic drive unit remains unlocked.

[0024] S6: The robot's left foot touches the ground, entering the double-leg support phase; at this time, the hydraulic drive units of both legs of the robot are locked, and neither leg can move up or down;

[0025] S7: The bi-leg gait cycle consisting of steps S1 to S6 can enable the robot to walk forward.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention utilizes a hydraulic drive unit for static support, while a motor provides power during movement. This maintains the high precision and simple control characteristics of motor-driven legged robots. Simultaneously, this invention transfers the load originally borne by the motor to the hydraulic drive unit, which then bears the load, significantly improving the load-bearing capacity of the legged robot. The static support unit and the power drive unit are separated and do not interfere with each other, ensuring flexibility during movement and decoupling the control of the hydraulic drive unit and the motor, further reducing control costs. This invention uses fewer hydraulic mechanisms overall, resulting in a lighter overall weight. Attached Figure Description

[0028] Figure 1 This is a simplified diagram of the single-leg mechanical structure of the legged robot described in this invention;

[0029] Figure 2This is a three-dimensional structural diagram of a single leg of the legged robot described in this invention;

[0030] Figure 3 This is a static support force analysis diagram of the legged robot described in this invention;

[0031] Figure 4 This is a diagram showing the change in the length of the hydraulic cylinder during the longitudinal movement of the leg of the legged robot described in this invention.

[0032] Figure 5 This is a single-leg gait cycle diagram of the legged robot described in this invention.

[0033] The attached diagram is labeled as follows: 1. Lower leg rod, 2. Thigh rod, 3. Thigh parallel rod, 4. Lower leg parallel rod, 5. Lower leg steering rod, 6. Thigh steering rod, 7. Lower leg slider connecting rod, 8. Thigh slider, 9. Lower leg slider, 10. Hydraulic drive unit, 11. Detailed Implementation

[0034] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0035] like Figure 1 and 2 As shown, this invention provides a high-load legged robot based on hydrostatic support. The robot mainly includes a left leg and a right leg. The left and right legs have identical structures and each includes a lower leg rod 1, a thigh rod 2, a thigh parallel rod 3, a lower leg parallel rod 4, a lower leg steering rod 5, a thigh steering rod 6, a lower leg slider connecting rod 7, a thigh slider connecting rod 8, a thigh slider 9, a lower leg slider 10, and a hydraulic drive unit 11. Furthermore, as... Figure 1 As shown, it also has hinge joints a, b, c, d, e, f, g, h and a contact point i between the toe (located at the lower end of the lower leg bar 1) and the ground.

[0036] The following section will use a single leg as an example to explain the structure and connection method of specific components.

[0037] In this invention, the upper end of the calf rod 1 is hinged to the lower end of the thigh rod 2, and the upper end of the thigh rod 2 is hinged to the upper ends of the calf parallel rod 4 and the calf turning rod 5. The upper ends of the calf parallel rod 4 and the calf turning rod 5 are fixedly connected. The upper end of the thigh rod 2 is fixedly connected to the upper end of the thigh turning rod 6. That is to say, both the thigh rod 2 and the calf parallel rod 4 can rotate freely around the hinge joint d, and during the rotation, the angle between the thigh rod 2 and the thigh turning rod 6 remains unchanged, as does the angle between the calf parallel rod 4 and the calf turning rod 5.

[0038] In this embodiment, the angle between the thigh rod 2 and the thigh steering rod 6 is relatively constant, and the angle between the lower leg parallel rod 4 and the lower leg steering rod 5 is relatively constant, and these two relative angles are equal.

[0039]

[0040] in, It is a constant angle value.

[0041] In this invention, the lower end of the thigh parallel rod 3 is hinged to the lower leg rod 1, and the upper end is hinged to the lower end of the lower leg parallel rod 4. In this embodiment, the thigh rod 2, thigh parallel rod 3, lower leg parallel rod 4, and the lower leg rod 1 located above the hinge point with the thigh parallel rod 3 together form a parallelogram (parallel four-bar linkage). That is, the distance between hinge joints ab is equal to the distance between hinge joints cd, and the distance between hinge joints ac is equal to the distance between hinge joints bd.

[0042] l ab =l cd

[0043] l ac =l bd

[0044] Among them, l ab l is the distance between the hinge joints ab. cd l is the distance between the hinge joints cd. ac l is the distance between the hinge joints ac. bd This is the distance between the hinge joints bd.

[0045] In this invention, one end of the calf slider connecting rod 7 is hinged to the lower end of the calf steering rod 5, and the other end is fixed with a calf slider 10 that can slide along the slide rail. One end of the thigh slider connecting rod 8 is hinged to the lower end of the thigh steering rod 6, and the other end is fixed with a thigh slider 9 that can slide along the slide rail. Along the driving direction, one end of the hydraulic drive unit 11 is fixedly connected to the calf slider 8, and the other end is fixedly connected to the thigh slider 9. That is, the hydraulic drive unit 11 can change the distance between the calf slider 10 and the thigh slider 9.

[0046] In this embodiment, the ratio of the lengths of the lower leg rod 1 and the lower leg steering rod 5 is equal to the ratio of the lengths of the thigh rod 2 and the thigh steering rod 6. That is:

[0047]

[0048] Among them, l ib l is the distance between the point of contact between the toe and the ground (i) and the hinge joint (d). dg l is the distance between the articulated joints dg. bd l is the distance between the articulated joints bd.df df represents the distance between the articulated joints.

[0049] In this embodiment, the sliding axes of the thigh slider 9 and the calf slider 10 coincide, and the upper end of the thigh rod 2 is also located on this axis, that is, the hinge joints d, e, and h are located on this axis. The angle between the sliding axes of the thigh slider 9 and the calf slider 10 and the vertical direction is also [value missing]. In such Figure 1 In one of the structures shown, It is 90°.

[0050] In this embodiment, the lower leg steering rod 5 and the lower leg slider connecting rod 7 are of equal length, and the thigh steering rod 6 and the thigh slider connecting rod 8 are of equal length, that is:

[0051] l df =l ef

[0052] l dg =l hg

[0053] Among them, l df l is the distance between the articulated joints df. ef l is the distance between the articulated joints ef. dg l is the distance between the articulated joints dg. hg hg is the distance between the hinge joints.

[0054] In this embodiment, the hydraulic drive unit 11 is installed between the thigh slider 9 and the lower leg slider 10, and can be a linear single-bar hydraulic cylinder or a pneumatic cylinder, etc. The maximum load of the hydraulic drive unit 11 should be greater than or equal to the average maximum load of a single leg of the robot. The ratio of k to the length of the lower leg rod 1 to the lower leg steering rod 5 is:

[0055]

[0056]

[0057] Among them, L h L is the maximum load of the hydraulic drive unit. a This represents the average maximum load per leg of the robot.

[0058] In practical use, when the vertical distance from the robot's toe to the axes of the two sliders on the thigh and lower leg is constant, the hydraulic circuit is closed, and the hydraulic drive unit is locked, maintaining a constant relative distance between the thigh and lower leg sliders as a rigid body. When the vertical distance from the robot's toe to the axes of the two sliders on the thigh and lower leg changes, the hydraulic circuit is opened, the hydraulic drive unit is unlocked, and the relative distance between the thigh and lower leg sliders can be arbitrarily changed. Figure 4As shown, the vertical distance from the robot body to the foot is proportional to the length of the hydraulic drive unit 11. The shorter the vertical distance from the body to the foot, the shorter the length of the hydraulic drive unit.

[0059] In this embodiment, the lower leg rod 1 and the upper leg rod 2 move independently, respectively, using a lower leg motor and an upper leg motor. Specifically, the lower leg motor allows the lower leg rod 1 to rotate around the hinge joint b in the direction of travel, and the upper leg motor allows the upper leg rod 2 to rotate around the hinge joint d in the direction of travel. When the motors are driving the movement, the hydraulic drive unit 11 is unlocked, allowing the distance between the upper leg slider 9 and the lower leg slider 10 to change freely.

[0060] like Figure 2 As shown, the motors for both the thigh and lower leg levers are located at hinge point d at the root of the thigh. The thigh lever motor directly drives the thigh lever to swing, while the lower leg lever motor drives the lower leg lever to swing via a parallel four-bar linkage. There is an offset between the physical thigh lever component and its theoretical axis; there is also an offset between the physical lower leg lever component and its theoretical axis. This offset setting increases the range of motion of the robot's legs.

[0061] This invention uses a hydraulic drive unit for static support, and its force analysis is as follows:

[0062] like Figure 3 As shown, for ease of explanation, each leg component of the robot is referred to by its two endpoints. For example, the thigh leg 2 is referred to as the bd leg, and other components are referred to similarly.

[0063] like Figure 3 As shown, the force F acting on the toes of the robot during static support is... G Vertically upward, with no lateral force.

[0064] like Figure 3 As shown, let the angle between rod bi and the vertical direction be α, the angle between rod bd and the vertical direction be β, and the vertical distance from the motor output shaft to the ground be H.

[0065] Easy to obtain:

[0066] H = l bi cosα+l bd cosβ

[0067] Among them, l bi Let l be the length of rod bi. bd Let be the length of rod bd. The lengths of other rods in the subsequent analysis will also be expressed in the same way.

[0068] Since rods ab and cd are parallel, it can be deduced that the angle between rod dc and the vertical direction is also α.

[0069] And because

[0070]

[0071] Let eh be the angle between the line and the vertical direction.

[0072] Therefore, we can conclude that:

[0073] ∠fde=α

[0074] ∠dgh=β

[0075] Based on the rod length condition l ef =l df , l dg =l hg We can obtain:

[0076] l ed =2l df cosα

[0077] l dh =2l dg cosβ

[0078] Based on the rod length condition:

[0079]

[0080] We can obtain:

[0081]

[0082] Based on the principle of virtual work, the following equation can be established:

[0083] F G δH+T up δ∠edb+T low δ∠cdh=0

[0084] Where δH is the virtual displacement of the toe in the vertical direction, and T up and T low The output torques are for the thigh and calf motors, respectively.

[0085] From the aforementioned geometric analysis, we can see that:

[0086]

[0087] Since the length of eh is adjusted by the length of the hydraulic cylinder, the length of eh remains constant when the hydraulic cylinder is closed. eh It is a constant.

[0088] That is:

[0089]

[0090] Therefore, when the hydraulic cylinder is closed and the length of eh is constant, the motor torque always satisfies the following:

[0091] T up δ∠edb+T low δ∠cdh=0

[0092] At this point, there is still one degree of freedom, which is the movement of the robot's toes on a level surface. Therefore, when the output torque of both motors is 0, the robot can still achieve self-support.

[0093] When a user uses the aforementioned high-load legged robot based on hydrostatic support, the single-leg gait cycle diagram is as follows: Figure 5 As shown. The specific control method within a single gait cycle is as follows:

[0094] S1: When the robot is in the left-leg support phase, it prepares to lift its right leg. At this time, the robot controls the left leg hydraulic drive unit 11 to lock, preventing the robot's left leg from moving up and down. The robot then controls the right leg hydraulic drive unit 11 to unlock. Subsequently, the robot lifts its right leg and enters a swinging motion, at which point the robot's right leg can move up and down.

[0095] S2: The robot's right leg swings forward. During this process, the robot's left leg hydraulic drive unit 11 remains locked, while the right leg hydraulic drive unit 11 remains unlocked.

[0096] S3: The robot's right foot touches the ground, entering the dual-leg support phase. At this time, the hydraulic drive units 11 of both legs of the robot are locked, and neither leg can move up or down.

[0097] S4: The robot enters the right leg support phase, preparing to lift its left leg. At this time, the robot locks the right leg hydraulic drive unit 11, preventing the robot's right leg from moving up and down. The robot then unlocks the left leg hydraulic drive unit 11. Subsequently, the robot lifts its left leg, entering a swinging motion, at which point the robot's left leg can move up and down.

[0098] S5: The robot's left leg swings forward. During this process, the robot's right leg hydraulic drive unit 11 remains locked, while the left leg hydraulic drive unit 11 remains unlocked.

[0099] S6: The robot's left foot touches the ground, entering the dual-leg support phase. At this time, the hydraulic drive units 11 of both legs of the robot are locked, and neither leg can move up or down.

[0100] S7: The bi-leg gait cycle consisting of steps S1 to S6 can enable the robot to walk forward.

[0101] This invention utilizes a hydraulic drive unit for static support, while a motor provides power during movement. This maintains the high precision and simple control characteristics of motor-driven legged robots. Simultaneously, this invention transfers the load originally borne by the motor to the hydraulic drive unit, which then bears the load, significantly improving the load-bearing capacity of the legged robot. The static support unit and the power drive unit are separated and do not interfere with each other, ensuring flexibility during movement and decoupling the control of the hydraulic drive unit and the motor, further reducing control costs. This invention uses fewer hydraulic mechanisms overall, resulting in a lighter overall weight.

[0102] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A high-load legged robot based on hydrostatic support, characterized by, The left leg and the right leg are identical in structure and each comprises a lower leg rod (1), a thigh rod (2), a thigh parallel rod (3), a lower leg parallel rod (4), a lower leg steering rod (5), a thigh steering rod (6), a lower leg slider connecting rod (7), a thigh slider connecting rod (8), a thigh slider (9), a lower leg slider (10) and a hydraulic drive unit (11); The upper end of the lower leg rod (1) is hingedly connected to the lower end of the thigh rod (2), the upper end of the thigh rod (2) is hingedly connected to the upper end of the lower leg parallel rod (4) and the upper end of the lower leg steering rod (5), the upper end of the lower leg parallel rod (4) and the upper end of the lower leg steering rod (5) are fixedly connected, the upper end of the thigh rod (2) is fixedly connected to the upper end of the thigh steering rod (6), the lower end of the thigh parallel rod (3) is hingedly connected to the lower leg rod (1), and the upper end of the thigh parallel rod (3) is hingedly connected to the lower end of the lower leg parallel rod (4), one end of the lower leg slider connecting rod (7) is hingedly connected to the lower end of the lower leg steering rod (5), and the other end of the lower leg slider connecting rod (7) is fixedly connected to the lower leg slider (10) which can slide along a slide rail, one end of the thigh slider connecting rod (8) is hingedly connected to the lower end of the thigh steering rod (6), and the other end of the thigh slider connecting rod (8) is fixedly connected to the thigh slider (9) which can slide along a slide rail, and one end of the hydraulic drive unit (11) is fixedly connected to the lower leg slider (10) in the driving direction, and the other end of the hydraulic drive unit (11) is fixedly connected to the thigh slider (9).

2. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The length ratio of the lower leg rod (1) to the lower leg steering rod (5) is equal to the length ratio of the thigh rod (2) to the thigh steering rod (6).

3. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The thigh rod (2), the thigh parallel rod (3), the lower leg parallel rod (4) and the lower leg rod (1) located at the upper part of the hinged connection with the thigh parallel rod (3) jointly form a parallelogram.

4. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The sliding axes of the thigh slider (9) and the lower leg slider (10) coincide, and the upper end of the thigh rod (2) is also located on the axis.

5. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The included angle between the thigh rod (2) and the thigh steering rod (6) and the included angle between the lower leg parallel rod (4) and the lower leg steering rod (5) are both φ.

6. The high-load legged robot based on hydrostatic support according to claim 5, characterized in that, The included angle between the sliding axes of the thigh slider (9) and the lower leg slider (10) and the vertical direction is also φ.

7. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The length of the lower leg steering rod (5) is equal to the length of the lower leg slider connecting rod (7), and the length of the thigh steering rod (6) is equal to the length of the thigh slider connecting rod (8).

8. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The maximum load of the hydraulic drive unit (11) is greater than or equal to the average single-leg maximum load of the robot k / 2 times, wherein k is the ratio of the length of the shank bar (1) to the length of the shank steering bar (5).

9. The high-load legged robot based on hydrostatic support according to claim 1, characterized in that, The lower leg rod (1) and the thigh rod (2) realize independent movement by means of a lower leg rod motor and a thigh rod motor respectively, and when the motors are driven to move, the hydraulic drive unit (11) is unlocked, so that the distance between the thigh slider (9) and the lower leg slider (10) can be freely changed.

10. A control method for a high-load legged robot based on hydrostatic support according to any one of claims 1 to 9, characterized in that, The specific implementation is as follows: S1: When the robot is in a left foot supporting period, the right foot is ready to be lifted; at this time, the robot controls the left leg hydraulic drive unit (11) to be locked, so that the robot left foot cannot move up and down; the robot controls the right leg hydraulic drive unit (11) to be unlocked; then the robot right foot is lifted, and enters a swing state, at this time, the robot right foot can move up and down; S2: The robot right leg swings forward; during this process, the robot left leg hydraulic drive unit (11) remains locked, and the right leg hydraulic drive unit (11) is always unlocked; S3: The robot right foot touches the ground, and enters the double foot support period; at this time, the hydraulic drive units (11) of the two legs of the robot are locked, and the two legs cannot move up and down; S4: The robot enters the right foot support period, and the left foot is ready to be lifted; at this time, the robot controls the right leg hydraulic drive unit (11) to be locked, and the right foot of the robot cannot move up and down; the robot controls the left leg hydraulic drive unit (11) to be unlocked; then the left foot of the robot is lifted, and enters the swing state, at this time the left foot of the robot can move up and down; S5: The left leg of the robot swings forward; during this process, the right leg hydraulic drive unit (11) of the robot remains locked, and the left leg hydraulic drive unit (11) is always unlocked; S6: The robot left foot touches the ground, and enters the double foot support period; at this time, the hydraulic drive units (11) of the two legs of the robot are locked, and the two legs cannot move up and down; S7: The double leg gait cycle composed of steps S1-S6 is cycled, and the forward walking of the robot can be realized.

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