CN114313050A

CN114313050A - Joint driving device and control method of wheel-leg robot and wheel-leg robot

Info

Publication number: CN114313050A
Application number: CN202111570477.XA
Authority: CN
Inventors: 胡小东; 刘辉; 徐彬; 秦也辰; 周俊杰
Original assignee: Beijing Institute of Technology BIT; Chongqing Innovation Center of Beijing University of Technology
Current assignee: Beijing Institute of Technology BIT; Chongqing Innovation Center of Beijing University of Technology
Priority date: 2021-12-21
Filing date: 2021-12-21
Publication date: 2022-04-12
Anticipated expiration: 2041-12-21
Also published as: CN114313050B

Abstract

The invention relates to the technical field of robots, in particular to a joint driving device and a control method of a wheel-leg robot and the wheel-leg robot. The purpose is to use wheeled mode motion as the owner, and simple step mode motion is assisted, and realization damping function that can be fine under wheeled mode, the flexible function of realization leg that can be fine under step mode to compromise flexibility and the functional of wheel leg robot in the in-service use process.

Description

Joint driving device and control method of wheel-leg robot and wheel-leg robot

Technical Field

The invention belongs to the technical field of robots, and particularly relates to a joint driving device and a control method of a wheel-leg robot and the wheel-leg robot.

Background

The wheel-leg robot is characterized in that wheels are added at the tail ends of the legs of the robot, the advantages of the wheels and the legs are fully combined, the robot can quickly and efficiently pass through a vehicle road surface, and can cross over an obstacle by using leg gait of the legs to realize passing under a non-structural environment. Compared with a foot robot, the wheel-leg robot has higher traveling speed and energy efficiency under a road environment, so that research on the wheel-leg robot is more and more focused.

At present, the wheel-leg robot is generally developed based on a four-foot or two-foot robot, the configuration of the leg joints of the wheel-leg robot is the same as that of a foot-type robot, the body and the load quality of the existing wheel-leg robot are low, the leg joints are driven by a motor, and the wheel-leg robot is mainly used for showing the control technology of the wheel-leg robot instead of aiming at practical application. Because the legged robot can only move in a step mode, in order to keep balance during movement, the legs generally have at least three joint actuators, namely a hip joint swing actuator, a hip joint rotation actuator and a knee joint rotation actuator, and the three joint actuators generally adopt flexible control to reduce impact force of the ground to the robot. Generally, for a light-load foot type robot (the total mass of a body and a load is less than or equal to 100kg), joint actuators of the robot generally adopt an electric transmission mode, and the specific types of the robot can be divided into three types, namely a direct drive motor, a motor reducer, an elastomer, a motor and a high reduction ratio reducer, wherein the elastomer is connected in series with the motor reducer; for a heavy-load foot type robot (the total mass of a body and a load is more than or equal to 100kg), a joint actuator of the robot generally adopts a hydraulic transmission mode, and the specific type is a servo valve control cylinder.

However, the heavy-load foot robot adopts a servo valve cylinder control actuator, and the two points have the following problems: 1. the wheel-leg robot, especially the heavy-duty wheel-leg robot, has larger volume and mass, and has higher energy utilization ratio compared with a foot type robot when the robot runs in a wheel type mode, so in order to realize the maximization of the energy benefit of the system, the heavy-duty wheel-leg robot mainly moves in a wheel type mode, and most of the actual road surface is flat, thus being suitable for the operation working condition of the wheel type mode; the walking mode of a heavy duty wheel-legged robot is only used to cross obstacles. Therefore, the heavy-duty wheel-leg robot and the foot-type robot have different working modes and different functional requirements on leg joints. The demand of a heavy duty wheeled legged robot for a leg joint actuator is similar to the demand of a vehicle for its chassis-i.e. good damping performance. Therefore, the joint configuration and the control mode of the existing foot type robot cannot meet the performance requirement; 2. the leg joint configuration of the existing wheel-leg robot is the same as that of a foot type robot, each leg is provided with three driving joints, and then joints for rolling wheels are added, so that each leg is provided with four joint degrees of freedom needing to be controlled, and the control difficulty is greatly increased; 3. at present, a servo valve control cylinder is adopted for a joint actuator of a heavy-load foot type robot, the hydraulic cylinder is controlled by throttling of the servo valve, accurate output force/speed control is realized, large throttling power loss exists, the transmission efficiency of a hydraulic system is low, and the effective energy utilization rate of the robot is low. If the leg joint actuator of the heavy-duty wheel-leg robot adopts a servo valve control cylinder, when the leg moves, a large amount of energy can be consumed, and the energy utilization rate of the robot is reduced.

Disclosure of Invention

In order to solve the above problems, the present invention provides a joint driving device for a wheel-legged robot, a control method, and a wheel-legged robot: on one hand, the working mode of the heavy-duty wheel-leg robot is better met, namely, wheel-type modal motion is taken as a main mode, simple step-type modal motion is taken as an auxiliary mode, the vibration reduction function can be well realized in the wheel-type mode, and the leg stretching function can be well realized in the step-type mode; on the other hand, each leg of the heavy-duty wheel-leg robot only comprises a hip joint rotary actuator, a knee joint rotary actuator and a hub motor, so that the hip joint swing actuator is removed, the number of the joint actuators is reduced, the control difficulty of the leg is reduced, and the complexity of the system is structurally reduced; in addition, the hip joint rotation actuator and the knee joint rotation actuator of the heavy-duty wheel leg robot both adopt an electro-hydrostatic closed loop, work based on a servo pump control principle, have higher transmission efficiency and higher force density ratio relative to a servo valve control cylinder actuator, and are matched with a link mechanism to output larger torque under smaller mass and volume.

The technical scheme adopted by the invention is as follows: the utility model provides a wheel leg robot's joint drive arrangement, includes hip joint rotary actuator, knee joint rotary actuator and motor, hip joint rotary actuator carries out displacement closed-loop control through hip joint electro-hydrostatic actuator and extends/contract, knee joint rotary actuator carries out displacement closed-loop control through knee joint electro-hydrostatic actuator and extends/contract, knee joint rotary actuator carries out power closed-loop control damping through knee joint electro-hydrostatic actuator, the motor drives the wheel through the controller and rotates/stops.

Preferably, the hip joint electro-hydrostatic actuator comprises a hip joint controller, a hip joint angular displacement sensor and a hip joint rotary actuator valve block, the hip joint controller is connected with the controller, and the hip joint controller controls the hip joint rotary actuator to extend/contract through the hip joint rotary actuator valve block; the hip joint angular displacement sensor is connected with the hip joint controller and arranged at the hinged position of the vehicle body and the thigh.

Preferably, two ends of the hip rotary joint actuator are respectively connected with the vehicle body and the thigh, the hip rotary joint actuator comprises a first hydraulic cylinder and a first piston rod, and the first piston rod is arranged in the first hydraulic cylinder and divides the first hydraulic cylinder into a first cavity and a second cavity; the hip joint rotary actuator valve block comprises a first oil way and a second oil way, and the first oil way and the second oil way are respectively communicated with the first cavity and the second cavity; the first piston rod alternately enters the first cavity and the second cavity through hydraulic oil to realize extension/contraction.

Preferably, the hip joint rotary actuator valve block further comprises a first motor, the first oil path and the second oil path are connected with a first hydraulic pump, and the first hydraulic pump is connected with the first motor; two-position two-way electromagnetic switch valves are arranged on the first oil way and the second oil way, and overflow valves are arranged on the first oil way and the second oil way.

Preferably, the knee joint electro-hydrostatic actuator comprises a knee joint controller, a knee joint angular displacement sensor and a knee joint rotation actuator valve block, the knee joint controller is connected with the controller, and the knee joint controller controls the extension/contraction of the knee joint rotation actuator through the knee joint rotation actuator valve block; the knee joint angular displacement sensor is connected with the knee joint controller and arranged at the hinged position of the thigh and the shank.

Preferably, two ends of the knee joint rotation actuator are respectively connected with the thigh and the shank, the knee joint rotation actuator comprises a second hydraulic cylinder and a second piston rod, and the second piston rod is arranged in the second hydraulic cylinder and divides the second hydraulic cylinder into a third cavity and a fourth cavity; the knee joint rotation actuator valve block comprises a third oil path and a fourth oil path, and the third oil path and the fourth oil path are respectively communicated with a third cavity and a fourth cavity; and the second piston rod alternately enters the third cavity and the fourth cavity through hydraulic oil to realize extension/contraction.

Preferably, the knee joint rotary actuator valve block further comprises a second motor, the third oil path and the fourth oil path are connected with a second hydraulic pump, and the second hydraulic pump is connected with the second motor; and overflow valves are arranged on the third oil way and the fourth oil way, and an energy accumulator is arranged on the third oil way or the fourth oil way.

Preferably, the knee joint electro-hydrostatic actuator further comprises a first pressure sensor and a second pressure sensor, the first pressure sensor is arranged on a third oil path, the second pressure sensor is arranged on a fourth oil path, and the first pressure sensor and the second pressure sensor are connected with the knee joint controller.

The control method of the wheel-legged robot joint driving device comprises the following steps:

in a flat road surface driving state: a hip joint rotary actuator and a knee joint rotary actuator of the wheel-leg robot are in a contraction state, a first piston rod on the hip joint rotary actuator is in a locking state, a second piston rod on the knee joint rotary actuator is in a force control vibration reduction position, the knee joint rotary actuator performs force closed-loop control vibration reduction through a knee joint electro-hydrostatic actuator, and a motor drives wheels to rotate through a controller;

in the obstacle road surface driving state: the motor is in a braking state through the controller, a first piston rod on the hip joint rotary actuator is in an unlocking state, and the hip joint rotary actuator and the knee joint rotary actuator respectively carry out displacement closed-loop control extension/contraction through a hip joint electro-hydrostatic actuator and a knee joint electro-hydrostatic actuator;

in a bumpy and undulating road running state: the first piston rod on the hip joint rotary actuator is in an unlocking state, the hip joint rotary actuator performs displacement closed-loop control extension/contraction through a hip joint electro-hydrostatic actuator, the knee joint rotary actuator performs force closed-loop control vibration reduction through a knee joint electro-hydrostatic actuator, and the motor drives the wheels to rotate through the controller.

Preferably, the hip joint electro-hydrostatic actuator and the knee joint electro-hydrostatic actuator both adjust the rotating speed of the corresponding motor through a PID algorithm.

A wheel-leg robot comprises a vehicle body, a controller, thighs, shanks and wheels; the bicycle comprises a bicycle body, a thigh, a hip joint rotary actuator, a knee joint rotary actuator, wheels and a motor, wherein the bicycle body is hinged with the thigh, the hip joint rotary actuator is connected between the bicycle body and the thigh, the knee joint rotary actuator is connected between the thigh and the shank, the wheels are arranged on the shank, and the wheels are driven to rotate through the motor.

The invention has the advantages that:

1) compared with the existing wheel-leg robot, the configuration and the control method of the joint actuator of the wheel-leg robot can better meet the requirements of various working modes by arranging the hip joint rotation actuator, the knee joint rotation actuator and the hub motor, namely the wheel-leg robot takes a wheel mode as a main part and takes a wheel-leg composite mode and a leg mode as an auxiliary part so as to deal with flat, obstacle and bumpy road surfaces; namely, the hip joint rotation actuator has the function of driving the hip joint to rotate by the extension and retraction of the actuator piston rod so as to control the hip joint to rotate to an instruction angle; the knee joint rotary actuator has the functions of telescopic driving of the knee joint and vibration reduction, the vibration reduction function can ensure the stability of the vehicle body of the wheel-leg robot in a wheel type driving mode and a wheel-leg composite mode, and the telescopic function ensures the requirements in a walking mode;

2) compared with the existing wheel-leg robot, the wheel-leg robot provided by the invention has the advantages that each leg is provided with three joint actuators, namely a hip joint rotation actuator, a knee joint rotation actuator and a hub motor, and compared with the existing wheel-leg robot in the configuration of the joint actuators, the number of the joint actuators of each leg is reduced, so that the structural complexity of the wheel-leg robot is reduced, and the difficulty of controlling each leg is reduced;

3) the joint actuator provided by the invention adopts an electro-hydrostatic closed loop scheme, works based on a servo pump control principle, combines the advantages of flexibility and convenience in electric drive control and hydraulic high power density ratio, has high force density ratio and good impact resistance, has high transmission efficiency and no throttling loss due to no valve control throttling loss, and improves the efficiency of the joint actuator while ensuring the high force density ratio of the joint actuator especially for a heavy-load wheel leg robot.

Drawings

FIG. 1 is a schematic view of the present invention and the movement of different road surfaces;

FIG. 2 is a schematic diagram of the operation of the hip joint rotary actuator;

FIG. 3 illustrates a hip joint rotary actuator control method;

FIG. 4 is a schematic diagram of the operation of the knee joint rotation actuator;

fig. 5 illustrates a knee joint rotation actuator control method.

In the figure: 1-a vehicle body; 2-a controller; 3-thigh; 4-shank; 5-hip revolute joint; 6-knee revolute joint; 7-hip joint angular displacement sensor; 8-knee angular displacement sensor; 9-hip joint rotation actuator; 10-knee joint rotation actuator; 11-a first hydraulic cylinder; 12-hip joint rotary actuator valve block; 13-a first piston rod; 14-a second hydraulic cylinder; 15-knee joint rotary actuator valve block; 16-a second piston rod; 17-a spring; 18-a motor; 19-a first electric machine; 20-a first hydraulic pump; 21-two-position two-way electromagnetic switch valve; 22-relief valve; 23-a first pressure sensor; 24-an accumulator; 25-a second pressure sensor; 26-a first cavity; 27-a second cavity; 28-a first oil path; 29-a second oil passage; 30-a third cavity; 31-a fourth cavity; 32-a third oil path; 33-a fourth oil path; 34-a second motor; 35-second hydraulic pump.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1-5, the robot is a wheel-leg robot, which mainly comprises a vehicle body 1, a controller 2, a thigh 3, a shank 4, a hip revolute joint 5 and a knee revolute joint 6, wherein the hip revolute joint 5 is formed at the position where the vehicle body 1 is articulated with the thigh 3, the knee revolute joint 6 is formed at the position where the thigh 3 is articulated with the shank 4, a wheel is connected with the shank 4, and the wheel is controlled by a motor 18 to rotate. The wheel-legged robot may have two or three or four legs, only one leg being illustrated in fig. 1.

The hip angular displacement sensor 7 is used for measuring the angular displacement at the hip rotary joint 5, and the knee angular displacement sensor 8 is used for measuring the angular displacement at the knee rotary joint 6.

The joint driving device of the wheel-leg robot comprises a hip joint rotary actuator 9, a knee joint rotary actuator 10 and a motor 18, wherein the hip joint rotary actuator 9 performs displacement closed-loop control extension/contraction through a hip joint electro-hydrostatic actuator, the knee joint rotary actuator 10 performs displacement closed-loop control extension/contraction through a knee joint electro-hydrostatic actuator, the knee joint rotary actuator 10 performs force closed-loop control vibration reduction through the knee joint electro-hydrostatic actuator, and the motor 18 drives wheels to rotate/stop through a controller 2.

The two ends of the hip joint rotary actuator 9 are respectively connected with the vehicle body 1 and the thigh 3, the hip joint rotary actuator 9 comprises a first hydraulic cylinder 11 and a first piston rod 13, the first piston rod 13 is arranged in the first hydraulic cylinder 11 and divides the first hydraulic cylinder 11 into a first cavity 26 and a second cavity 27, the rotation of the hip rotary joint 5 can be realized through the telescopic motion of the first piston rod 13, and the hip joint electro-hydrostatic actuator drives the first piston rod 13 to stretch through displacement closed-loop control, so that the extension or contraction of the hip joint actuator 9 is realized.

The two ends of the knee joint rotation actuator 10 are respectively connected with the thigh 3 and the shank 4, the knee joint rotation actuator 10 comprises a second hydraulic cylinder 14 and a second piston rod 16, and the second piston rod 16 is arranged in the second hydraulic cylinder 14 and divides the second hydraulic cylinder 14 into a third cavity 30 and a fourth cavity 31; the extension and contraction of the second piston rod 16 drives the knee rotary joint 6 to rotate, a spring 17 is sleeved on the second piston rod 16, one end of the spring 17 is fixedly arranged on the second hydraulic cylinder 14, and the other end of the spring 17 is arranged at the hinge position of the shank 4, so that the vibration reduction effect is provided; the knee joint electro-hydrostatic actuator drives the second piston rod 16 to extend and retract through displacement closed-loop control, so that the extension or retraction of the knee joint rotary actuator 10 is realized; the knee joint rotary actuator 10 can also perform force closed-loop control through a knee joint electro-hydrostatic actuator, so that vibration reduction is realized, and a wheel leg robot has a good vibration reduction effect when running on a bumpy road surface, the motor 18 drives the wheels to rotate/stop through the controller 2, the motor 18 is installed at the tail ends of the legs 4, and the rotation of the motor 18 drives the wheels to roll, so that the vehicle body 1 advances.

The hip joint electro-hydrostatic actuator comprises a hip joint controller, a hip joint angular displacement sensor 7 and a hip joint rotary actuator valve block 12, the hip joint controller is connected with the controller 2, and the hip joint controller controls the hip joint rotary actuator 9 to extend/contract through the hip joint rotary actuator valve block 12; the hip joint angular displacement sensor 7 is connected with the hip joint controller, and the hip joint angular displacement sensor 7 is arranged at the hinged position of the vehicle body 1 and the thigh 3.

The valve block 12 of the hip joint rotation actuator comprises a first oil path 28 and a second oil path 29, wherein the first oil path 28 and the second oil path 29 are respectively communicated with the first cavity 26 and the second cavity 27; the first piston rod 13 is extended/contracted by alternately entering the first cavity 26 and the second cavity 27 with hydraulic oil.

The hip joint rotation actuator valve block 12 further comprises a first motor 19, the first oil path 28 and the second oil path 29 are connected with a first hydraulic pump 20, and the first hydraulic pump 20 is connected with the first motor 19; two-position two-way electromagnetic switch valves 21 are arranged on the first oil way 28 and the second oil way 29, and overflow valves 22 are arranged on the first oil way 28 and the second oil way 29. The first motor 19 drives the first hydraulic pump 20 to rotate, so that the first hydraulic pump 20 sucks low-pressure oil and discharges high-pressure oil, the first hydraulic pump 20 is communicated with a first cavity 26 and a second cavity 27 of the first hydraulic cylinder 11 through a first oil path 28 and a second oil path 29, and a first piston rod 13 is in an unlocking or locking state through the communication or disconnection of the two-position two-way electromagnetic switch valve 21, the first hydraulic cylinder 11 is a double-piston-rod hydraulic cylinder, when the two-position two-way electromagnetic switch valve 21 on the first oil path 28 and the second oil path 29 is in an open position, the first piston rod 13 is in a locking state, the hip rotary joint 5 is locked at the moment and cannot rotate, and the angle between the thigh 3 and the vehicle body 1 is unchanged; when the two-position two-way electromagnetic switch valve 21 on the first oil path 28 and the second oil path 29 is in a communicating position, the output flow of the first hydraulic pump 20 can be adjusted by controlling the rotating speed of the first motor 19, so as to control the extension and contraction of the first piston rod 13 and drive the hip rotary joint 5 to rotate. The relief valve 22 serves as a relief valve to prevent the pressure in the first hydraulic cylinder 11 from exceeding a certain set pressure value, and pressure sensors for measuring the pressures in both chambers of the first hydraulic cylinder 11 may be additionally provided in the first oil passage 28 and the second oil passage 29.

The knee joint electro-hydrostatic actuator comprises a knee joint controller, a knee joint angular displacement sensor 8 and a knee joint rotation actuator valve block 15, the knee joint controller is connected with the controller 2, and the knee joint controller controls the extension/contraction of the knee joint rotation actuator 10 through the knee joint rotation actuator valve block 15; the knee joint angular displacement sensor 8 is connected with a knee joint controller, and the knee joint angular displacement sensor 8 is arranged at the hinged position of the thigh 3 and the shank 4.

The knee joint rotation actuator valve block 15 comprises a third oil path 32 and a fourth oil path 33, and the third oil path 32 and the fourth oil path 33 are respectively communicated with the third cavity 30 and the fourth cavity 31; the second piston rod 16 is alternately extended/contracted by hydraulic oil entering the third chamber 30 and the fourth chamber 31.

The knee joint rotation actuator valve block 15 further comprises a second motor 34, the third oil path 32 and the fourth oil path 33 are connected with a second hydraulic pump 35, and the second hydraulic pump 35 is connected with the second motor 34; the third oil passage 32 and the fourth oil passage 33 are provided with a relief valve 22, and the third oil passage 32 or the fourth oil passage 33 is provided with an accumulator 24. The second hydraulic cylinder 14 is a single-piston-rod hydraulic cylinder, one end of the spring 17 is fixed on the cylinder barrel of the second hydraulic cylinder 14, and the other end of the spring 17 is fixed on the lower leg 4, so that the spring 17 extends and contracts along with the second piston rod 16, the output flow of the second hydraulic pump 35 can be adjusted by controlling the rotating speed of the second motor 34, and the second piston rod 16 extends and contracts to drive the knee rotary joint 6 to rotate. In the embodiment, preferably, the accumulator 24 is disposed on an oil path connecting the rodless chamber, and when the second piston rod 16 extends, the second hydraulic pump 35 sucks the oil in the rod chamber of the second hydraulic cylinder 14 and discharges the high-pressure oil into the rodless chamber of the second hydraulic cylinder 14, and since the volume of the oil required in the rodless chamber is greater than the volume of the oil sucked from the rod chamber, the redundant oil is discharged from the accumulator 24 into the rodless chamber; when the second piston rod 16 retracts, the second hydraulic pump 35 sucks low-pressure oil from the rodless chamber of the second hydraulic cylinder 14 and discharges the low-pressure oil into the rod chamber of the second hydraulic cylinder 14, and since the volume of the oil required in the rod chamber is smaller than the volume of the oil sucked from the rodless chamber, the excess oil sucked from the rodless chamber is discharged into the accumulator 24, so that it can be seen that the accumulator 24 is required to compensate for the asymmetry of the volumes of the oil in the two chambers of the second hydraulic cylinder 14.

The knee joint electro-hydrostatic actuator further comprises a first pressure sensor 23 and a second pressure sensor 25, the first pressure sensor 23 and the second pressure sensor 25 are connected with a knee joint controller, the first pressure sensor 23 is arranged on the third oil path 32, and the second pressure sensor 25 is arranged on the fourth oil path 33.

The controller 2 sends a force instruction to the knee joint controller, the force instruction is a requirement for the output force of the knee joint rotation actuator 10 for realizing the vibration reduction of the vehicle body 1, the knee joint controller outputs a corresponding driving current to drive the second motor 34 to rotate after receiving the force instruction, the rotation torque of the second motor 34 drives the second hydraulic pump 35 to rotate and output high-pressure oil liquid with certain pressure, thereby changing the pressure of the two cavities of the second hydraulic cylinder 14, the pressure value is detected by the first pressure sensor 23 and the second pressure sensor 25, the actual output force of the second piston rod 16 acting on the shank 4 can be calculated after comparison and calculation, the output current is regulated by a PID algorithm after the actual output force is compared with the force instruction in the knee joint controller, thereby, the output force closed-loop control of the knee joint rotation actuator 10 is formed, and the target of the force closed-loop control is to reduce the vehicle body vibration.

The method for controlling a wheel-legged robot in the joint driving device for a wheel-legged robot includes:

in a flat road surface driving state: a hip joint rotation actuator 9 and a knee joint rotation actuator 10 of the wheel-legged robot are in a contraction state, a first piston rod 13 on the hip joint rotation actuator 9 is in a locking state, a second piston rod 16 on the knee joint rotation actuator 10 is in a force control vibration reduction position, the knee joint rotation actuator 10 performs force closed-loop control through a knee joint electro-hydrostatic actuator to achieve vibration reduction, and a motor 18 drives wheels to rotate through a controller 2.

Under a general road condition, as shown in fig. 1 (c), in order to obtain a fast traveling speed and a high energy utilization rate for the wheel-leg robot, the wheel-leg robot will operate in a wheeled vehicle mode, and the first piston rod 13 of the hip joint rotary actuator 9 is fully retracted, and the angular displacement of the hip rotary joint 5 is minimized; the second piston rod 16 of the knee joint rotation actuator 10 is close to the fully retracted position but can continue to move in the retracted direction. The control method of each joint of the wheel-type modal lower wheel-leg robot is as follows: first, the first piston rod 13 of the hip joint rotation actuator 9 is fully retracted and the hip joint 5 is locked. The method is mainly implemented by the following steps that as shown in fig. 2, the upper computer controller 2 controls the two-position two-way electromagnetic switch valves 21 to work at a conducting position, so that the first hydraulic cylinder 11 is communicated with the first hydraulic pump 20, the first motor 19 is controlled to rotate anticlockwise, the first hydraulic pump 20 sucks oil from a lower cavity of the first hydraulic cylinder 11 and discharges the oil into an upper cavity, and the first piston rod 13 is completely retracted. When the first piston rod 13 is completely retracted, the two-position two-way electromagnetic switch valves 21 are controlled to work at a stop position, and the hip rotary joint 5 is locked; next, the second piston rod 16 of the knee joint rotation actuator 10 moves to a force control damping position (a position away from the bottom of the second hydraulic cylinder 14, indicated by a broken line of the second piston rod 16 in fig. 4), and then operates in a force control damping mode under the control of the upper computer controller 2. The force control damping mode is realized by that, as shown in fig. 4, under the action of the gravity of the vehicle body 1, the rodless cavity high-pressure oil of the second hydraulic cylinder 14 drives the second motor 34 to rotate so as to retract the second piston rod 16, and when the second piston rod reaches the force control damping position, the upper computer controller 2 controls the second motor 34 to stop rotating so as to enable the height of the vehicle body to reach the height shown in (c) in fig. 1; then, the controller 2 controls the hub motor 18 to rotate, so that the wheel-legged robot moves forward in a wheel mode, and meanwhile, the knee joint rotation actuator 10 enters a force control vibration damping control mode, as shown in fig. 5, the upper computer controller 2 sends a force command to the knee joint controller, the force command is a request for the output force of the knee joint rotation actuator 10 for realizing vibration damping of the vehicle body 1, the knee joint controller outputs a corresponding driving current to drive the second motor 34 to rotate after receiving the force command, the rotating torque of the second motor 34 drives the second hydraulic pump 35 to rotate to output high-pressure oil liquid with certain pressure, so that the pressure of two cavities of the second hydraulic cylinder 14 is changed, the pressure value is detected by the first pressure sensor 23 and the second pressure sensor 25, and the actual output force of the second piston rod 16 acting on the lower leg 4 can be calculated through comparison, the actual output force is compared with the force command in the knee joint controller, and the output current is adjusted by the PID algorithm, thereby forming the closed-loop control of the output force of the knee joint rotation actuator 10, and the closed-loop control of the force is aimed at reducing the vehicle body vibration. The knee joint angular displacement sensor 8 detects the angular displacement of the knee rotary joint 6 at any moment and transmits the angular displacement to the knee joint controller so as to monitor the knee joint angle and prevent the second piston rod 16 from moving to the stroke end position of the second hydraulic cylinder 14 to collide with the cylinder body.

In the obstacle road surface driving state: the motor 18 is in a braking state through the controller 2, the first piston rod 13 on the hip joint rotation actuator 9 is in an unlocking state, and the hip joint rotation actuator 9 and the knee joint rotation actuator 10 respectively carry out displacement closed-loop control through a hip joint electro-hydrostatic actuator and a knee joint electro-hydrostatic actuator to realize extension/contraction.

When a road surface with an obstacle, such as the road surface shown in fig. 1 (b), and a wheel cannot pass through, the wheel-leg robot needs to work in a walking mode, such as the configuration shown in fig. 1 (b), and at this time, the hip joint rotation actuator 9 and the knee joint rotation actuator 10 both adopt displacement closed-loop control, and the first piston rod 13 and the second piston rod 16 thereof need to perform telescopic motion within the working stroke range according to the gait control. The control method of each joint of the walking type modal lower wheel-leg robot is as follows: two-position two-way electromagnetic switch valves 21 in the hip joint rotary actuator 9 work at a conducting position under the control of the controller 2, so that the first hydraulic pump 20 is communicated with the first hydraulic cylinder 11; under the step mode, the controller 2 respectively sends an angular displacement track instruction to the hip joint rotation actuator 9 and the knee joint rotation actuator 10, the hip/knee joint controller outputs corresponding current to drive the corresponding motors to rotate after receiving the instruction, the corresponding hydraulic pumps suck and discharge oil in two cavities of the hydraulic cylinders to extend or retract piston rods, the same hydraulic pumps suck and discharge oil in two cavities of the hydraulic cylinders to extend or retract piston rods, the hip rotary joint 5 and the knee rotary joint 6 rotate to expected angular displacement through the connecting rod action of thighs 3 and 4, the hip/knee rotation angle displacement sensor detects the actual angular displacement and feeds the actual angular displacement back to the hip/knee joint controller to be compared with the angular displacement instruction, the rotating speed of the corresponding motors is adjusted through a PID algorithm, the actual angular displacement is changed along with the angular displacement instruction, and accordingly displacement closed-loop control of the hip/knee joint rotation actuator is formed, the joint trajectory tracking requirement under the step mode is met, and the pressure sensor is used for monitoring the state of the hip/knee rotary joint actuator at the moment. At this time, the in-wheel motor 18 operates in a braking state to inhibit the wheel from rolling.

In a bumpy and undulating road running state: the first piston rod 13 on the hip joint rotary actuator 9 is in an unlocking state, the hip joint rotary actuator 9 performs displacement closed-loop control through a hip joint electro-hydrostatic actuator to realize extension/contraction, the knee joint rotary actuator 10 performs closed-loop control through a knee joint electro-hydrostatic actuator to realize vibration reduction, and the motor 18 drives the wheels to rotate through the controller 2.

When a road surface with a continuous undulating gradient is encountered, as shown in (a) in fig. 1, the wheel-leg robot cannot pass through the road surface quickly in a wheel-type mode, and at the same time, the wheel-leg robot should work in a wheel-leg composite mode to pass through the road surface slowly to ensure the stability of the wheel-leg robot, as shown in (a) in fig. 1, the hip rotary joint 5 is not locked, the hip rotary actuator 9 adopts displacement closed-loop control, and the knee rotary actuator 10 adopts force closed-loop control, so that the vibration reduction of the vehicle body in the wheel-leg composite mode is realized, compared with the wheel-type mode, because the legs are not completely contracted in the wheel-leg composite mode, the height of the vehicle body relative to the ground plane is high, the gravity center of the whole wheel-leg robot is high, and the dynamic balance control difficulty is high during the quick running, so that the wheel-leg robot can only run at a low speed in the wheel-leg composite mode. Under the wheel-leg composite mode, the control method of each joint is as follows: the hip joint rotation actuator 9 adopts a displacement closed-loop control strategy, as shown in fig. 3, at this time, two-position two-way electromagnetic switch valves 21 work at a conducting position under the control of the controller 2, and the first hydraulic pump 20 is communicated with two cavities of the first hydraulic cylinder 11. The upper computer controller 2 sends an angular displacement instruction to the hip joint controller, then drives the first motor 19 to rotate, the first hydraulic pump 20 rotates to enable the first piston rod 13 of the first hydraulic cylinder 11 to extend or retract, so that the hip rotary joint 5 rotates, the hip joint angular displacement sensor 7 measures the hip joint angular displacement, transmits the hip joint angular displacement to the hip joint controller, compares the hip joint angular displacement with the angular displacement instruction, and adjusts the rotating speed of the first motor 19 through a PID algorithm to enable the actual angular displacement of the hip rotary joint 5 to change along with the angular displacement instruction; the knee joint rotation actuator 10 adopts a force closed-loop control strategy, as shown in fig. 5, the controller 2 sends a force tracking command to the knee joint controller, the knee joint controller outputs current to drive the second motor 34 to rotate, the second hydraulic pump 35 rotates to enable the second piston rod 16 of the second hydraulic cylinder 14 to extend or retract, so that the knee joint rotation joint 6 rotates, the pressure of two cavities of the second hydraulic cylinder 14 is detected through the first pressure sensor 23 and the second pressure sensor 25, the actual output force of the knee joint rotation actuator 10 is calculated and then transmitted to the knee joint controller, and compared with the force command, the magnitude of the output current is adjusted through a PID algorithm, so that the output force of the knee joint rotation actuator 10 follows the change of the force command; the hub motor 18 rotates slowly under the control of the controller 2, thereby advancing the wheel-legged robot slowly. Under the wheel-leg composite mode, the wheel-leg robot has a higher height of a vehicle body relative to the wheel-leg composite mode, so that the robot can only run at a low speed, and the better vibration reduction effect can be achieved by adopting the force closed-loop control of the knee rotary joint actuator and the displacement closed-loop control of the hip rotary joint actuator.

The invention discloses a control method of each joint of a wheel-leg robot, which operates in different modes: in the wheel mode, the first piston rod 13 of the hip joint rotary joint actuator 9 is completely contracted, the two-position two-way electromagnetic switch valves 21 work at a cut-off position to lock the rotary motion of the hip joint, and the hip joint cannot rotate; the second piston rod 16 of the knee joint rotation actuator 10 is contracted to a certain position, and the knee joint rotation actuator 10 adopts force-based closed-loop control to realize the vibration reduction function and ensure the stability of the vehicle body; the motor 18 operates to drive the wheels to roll to advance the vehicle body rapidly. Under the step mode, the hip joint rotary actuator 9 and the knee joint rotary actuator 10 both work in the telescopic function, and the space trajectory tracking is realized by adopting the closed-loop control based on the angular displacement; while the motor 18 is in a braking condition to inhibit the wheel from rolling. Under the wheel-leg composite mode, the hip joint rotation actuator 9 adopts closed-loop control based on angular displacement, and realizes hip joint rotation through the extension and retraction of a first piston rod 13 of the hip joint rotation actuator so as to realize the adjustment of the height of the vehicle body; the knee joint rotary actuator 10 adopts force-based closed-loop control to realize vibration reduction of the vehicle body 1 so as to ensure the stability of the vehicle body in a wheel-leg composite mode; the motor 18 drives the wheels to roll, so that the vehicle body advances slowly.

The above embodiments are preferred embodiments, it should be noted that the above preferred embodiments should not be considered as limiting the invention, and the scope of protection of the invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.

Claims

1. A joint driving device of a wheel-legged robot, characterized in that: the device comprises a hip joint rotary actuator (9), a knee joint rotary actuator (10) and a motor (18), wherein the hip joint rotary actuator (9) performs displacement closed-loop control extension/contraction through a hip joint electro-hydrostatic actuator, the knee joint rotary actuator (10) performs displacement closed-loop control extension/contraction through a knee joint electro-hydrostatic actuator, the knee joint rotary actuator (10) performs force closed-loop control vibration reduction through the knee joint electro-hydrostatic actuator, and the motor (18) drives wheels to rotate/stop through a controller (2).

2. The joint driving apparatus of a robot with wheel legs according to claim 1, wherein: the hip joint electro-hydrostatic actuator comprises a hip joint controller, a hip joint angular displacement sensor (7) and a hip joint rotary actuator valve block (12), the hip joint controller is connected with the controller (2), and the hip joint controller controls the hip joint rotary actuator (9) to extend/contract through the hip joint rotary actuator valve block (12); the hip joint angular displacement sensor (7) is connected with the hip joint controller, and the hip joint angular displacement sensor (7) is arranged at the hinged position of the car body (1) and the thigh (3).

3. The joint driving apparatus of a robot with wheel legs according to claim 2, wherein: the two ends of the hip rotary joint actuator (9) are respectively connected with the car body (1) and the thigh (3), the hip rotary joint actuator (9) comprises a first hydraulic cylinder (11) and a first piston rod (13), and the first piston rod (13) is arranged in the first hydraulic cylinder (11) and divides the first hydraulic cylinder (11) into a first cavity (26) and a second cavity (27); the hip joint rotary actuator valve block (12) comprises a first oil path (28) and a second oil path (29), and the first oil path (28) and the second oil path (29) are respectively communicated with a first cavity (26) and a second cavity (27); the first piston rod (13) alternately enters the first cavity (26) and the second cavity (27) through hydraulic oil to realize expansion/contraction.

4. The joint driving apparatus of a robot with wheel legs according to claim 3, wherein: the hip joint rotary actuator valve block (12) further comprises a first motor (19), the first oil path (28) and the second oil path (29) are connected with a first hydraulic pump (20), and the first hydraulic pump (20) is connected with the first motor (19); two-position two-way electromagnetic switch valves (21) are arranged on the first oil way (28) and the second oil way (29), and overflow valves (22) are arranged on the first oil way (28) and the second oil way (29).

5. The joint driving apparatus of a robot with wheel legs according to claim 1, wherein: the knee joint electro-hydrostatic actuator comprises a knee joint controller, a knee joint angular displacement sensor (8) and a knee joint rotation actuator valve block (15), the knee joint controller is connected with the controller (2), and the knee joint controller controls the extension/contraction of the knee joint rotation actuator (10) through the knee joint rotation actuator valve block (15); the knee joint angular displacement sensor (8) is connected with a knee joint controller, and the knee joint angular displacement sensor (8) is arranged at the hinged position of the thigh (3) and the shank (4).

6. The joint driving apparatus of a robot with wheel legs according to claim 5, wherein: the knee joint rotation actuator (10) is connected with the thigh (3) and the shank (4) at two ends respectively, the knee joint rotation actuator (10) comprises a second hydraulic cylinder (14) and a second piston rod (16), and the second piston rod (16) is arranged in the second hydraulic cylinder (14) and divides the second hydraulic cylinder (14) into a third cavity (30) and a fourth cavity (31); the knee joint rotary actuator valve block (15) comprises a third oil path (32) and a fourth oil path (33), and the third oil path (32) and the fourth oil path (33) are respectively communicated with a third cavity (30) and a fourth cavity (31); the second piston rod (16) alternately enters the third cavity (30) and the fourth cavity (31) through hydraulic oil to realize extension/contraction.

7. The joint driving apparatus of a robot with wheel legs according to claim 6, wherein: the knee joint rotary actuator valve block (15) further comprises a second motor (34), the third oil path (32) and the fourth oil path (33) are connected with a second hydraulic pump (35), and the second hydraulic pump (35) is connected with the second motor (34); and overflow valves (22) are arranged on the third oil way (32) and the fourth oil way (33), and an energy accumulator (24) is arranged on the third oil way (32) or the fourth oil way (33).

8. The joint driving apparatus of a robot with wheel legs according to claim 7, wherein: the knee joint electro-hydrostatic actuator further comprises a first pressure sensor (23) and a second pressure sensor (25), the first pressure sensor (23) is arranged on the third oil path (32), the second pressure sensor (25) is arranged on the fourth oil path (33), and the first pressure sensor (23) and the second pressure sensor (25) are connected with a knee joint controller.

9. The method for controlling a robot joint driving apparatus of a wheel-legged robot according to any one of claims 1 to 8, characterized by comprising:

in a flat road surface driving state: a hip joint rotary actuator (9) and a knee joint rotary actuator (10) of the wheel-legged robot are in a contraction state, a first piston rod (13) on the hip joint rotary actuator (9) is in a locking state, a second piston rod (16) on the knee joint rotary actuator (10) is in a force control vibration reduction position, the knee joint rotary actuator (10) performs force closed-loop control vibration reduction through a knee joint electro-hydrostatic actuator, and a motor (18) drives wheels to rotate through a controller (2);

in the obstacle road surface driving state: the motor (18) is in a braking state through the controller (2), a first piston rod (13) on the hip joint rotary actuator (9) is in an unlocking state, and the hip joint rotary actuator (9) and the knee joint rotary actuator (10) perform displacement closed-loop control extension/contraction through a hip joint electro-hydrostatic actuator and a knee joint electro-hydrostatic actuator respectively;

in a bumpy and undulating road running state: the first piston rod (13) on the hip joint rotary actuator (9) is in an unlocking state, the hip joint rotary actuator (9) performs displacement closed-loop control extension/contraction through a hip joint electro-hydrostatic actuator, the knee joint rotary actuator (10) performs force closed-loop control vibration reduction through the knee joint electro-hydrostatic actuator, and the motor (18) drives wheels to rotate through the controller (2).

10. The control method of a robot wheel-leg robot according to claim 9, characterized in that: the hip joint electro-hydrostatic actuator and the knee joint electro-hydrostatic actuator both adjust the rotating speed of the corresponding motor through a PID algorithm.

11. A wheel-legged robot including the joint driving apparatus of the wheel-legged robot according to any one of claims 1 to 8, characterized in that: comprises a vehicle body (1), a controller (2), thighs (3), shanks (4) and wheels; the bicycle is characterized in that the bicycle body (1) is hinged to the thigh (3), a hip joint rotary actuator (9) is connected between the bicycle body (1) and the thigh (3), a knee joint rotary actuator (10) is connected between the thigh (3) and the shank (4), wheels are arranged on the shank (4), and the wheels are driven to rotate through a motor (18).