Hydraulic drive foot robot joint control experiment table

Abstract

The application discloses a kind of hydraulic drive foot type robot joint control experiment table, belong to foot type robot field.The application transforms self-destructive full physical test into predictive research under laboratory conditions, accurately simulates complex and changeable force or torque load spectrum.In the research, the force loading test under fixed position and the force loading test under position change are carried out using the joint control experiment table, it is proved that after the position parameter of joint control cylinder valve is added in feedforward link, the load simulation cylinder can output the expected force curve;Then step position, sinusoidal position and high-low pressure energy-saving experiment are carried out on joint control system based on servo proportional valve and based on cartridge valve respectively, it is proved that compared with single high-pressure oil source control, using high-low pressure oil source can save 25%-38% energy.

Description

Technical Field

[0001] This invention belongs to the field of legged robots, specifically relating to a hydraulically driven legged robot joint control experimental platform. Background Technology

[0002] Hydraulic legged robots are a common type of mobile robot, boasting advantages such as high load-bearing capacity and explosive power. However, defects in any component or unit of a high-performance hydraulically driven legged robot can lead to serious problems, necessitating rigorous testing of the performance and quality of key components and units before assembly and integration. Traditional sensor calibration is merely static calibration; based on the calibration reports provided by vendors, only static parameters of displacement and force sensors can be obtained. Currently, there is no platform for performance testing of hydraulic servo drives in assembled legged robots. With the gradual maturation of hydraulically driven legged robot technology and the rapid development of the robot manufacturing industry, there is an urgent need for a platform for performance testing of hydraulic servo drives in assembled legged robots, meeting the specific requirements of robots for the high-speed response characteristics of hydraulic drive devices.

[0003] Chinese patent application CN102841 602A discloses a performance testing platform and method for the control development of a single-leg robot assembly. The platform includes a gantry-type three-coordinate robotic arm assembly, a robot leg connecting bracket, a Stewart platform, a six-dimensional force sensor, the single-leg robot assembly, and a five-dimensional force measurement platform. The Stewart platform integrates a servo controller and a displacement sensor. The Stewart platform is inverted and mounted on the base of the robot leg bracket. The five-dimensional force measurement platform is installed on the ground centered below the single-leg robot assembly. The robot leg connecting bracket is fixed to the Z-axis moving support frame assembly of the gantry-type three-coordinate robotic arm assembly. This single-leg assembly control development performance testing platform is mainly used for the development and research of single-leg movement and rapid gait control in biomimetic gait generation of legged robots, as well as multiple control strategies such as robot load distribution, control force distribution, single-leg force feedback control, and "off-road gait + continuous force control" posture stabilization control. The control strategy can be applied to the robot system on the premise that the hydraulic servo drive can operate normally and the motion characteristics are known. However, the test platform itself cannot be used to test the joint drive cylinders used for joint control of hydraulically driven legged robots.

[0004] In addition, Professor Kong Xiangdong's team at Yanshan University built a dual-channel counter-pressure test platform for the hydraulic drive unit of a quadruped robot. The mechanical part consists of two identical servo valve-controlled cylinder counter-pressure designs (Zhang Wei. Research on Redundant Force Suppression in Load Simulation System of Quadruped Robot Hydraulic Drive Unit [D]. Yanshan University, 2013). The hydraulic control part uses an axial piston pump to supply pressure to both the test end and the load end simultaneously, using a two-position three-way valve to control the on / off state and a servo proportional valve to control the direction. The measurement and control system directly uses the dspace DS1104 control board to collect data and control the hydraulic system.

[0005] In the development of hydraulic legged robots, it is necessary to test their performance in various aspects through full-scale on-site testing. However, on-site testing is time-consuming and costly, making it unsuitable for the early stages of development. Furthermore, the control performance, load capacity, power output, and continuous working time of a hydraulically driven legged robot largely depend on the performance and efficiency of its joint control system. Therefore, a method is needed to simulate various load conditions under real-world working conditions for the research and testing of the hydraulic joint control system. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a hydraulically driven legged robot joint control experimental platform. By utilizing electro-hydraulic load simulation equipment to simulate various load states experienced by the robot under real working conditions in a laboratory setting, the hydraulic joint control system can be studied and tested. This transforms the self-destructive full-body experiment into predictive research under laboratory conditions, enabling precise simulation of complex and variable force or torque load spectra. This achieves the goals of shortening the development cycle, saving costs, and improving reliability and success rate.

[0007] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0008] This invention provides a hydraulically driven legged robot joint control experimental platform for testing the joint drive cylinder used in the joint control of a hydraulically driven legged robot. The experimental platform includes a load simulation cylinder. In use, the load simulation cylinder and the joint drive cylinder to be tested are rigidly connected coaxially and top-to-top. A force sensor and a displacement sensor are provided at the shaft connection between the load simulation cylinder and the joint drive cylinder. The load simulation cylinder is connected to a first hydraulic control system for controlling the shaft movement of the load simulation cylinder. The first hydraulic control system includes a first oil tank, a load simulation pump, and a servo proportional valve. The servo proportional valve has hydraulic lines that communicate with the rodless chamber and the rod chamber of the load simulation cylinder, respectively, and the two hydraulic lines are connected through a damping hole.

[0009] The hydraulically driven legged robot joint control test bench of this invention consists of three parts: a joint control section, a load simulation section, and a measurement and control system. The joint control section is the test object, i.e., the joint control system used in the actual robot, which realizes the driving of the robot joints; while the load simulation section is used to simulate the actual working conditions of the robot and apply load to the joint control system; the test bench is equipped with a computer measurement and control system, which can complete the control of the joint control section and the load simulation section, measure their control performance and system energy consumption, and evaluate the system efficiency and performance.

[0010] The load simulation system is controlled by a servo proportional valve to operate the load simulation cylinder. To reduce hydraulic shock in the hydraulic system and improve the force control effect of the load simulation system, a damping orifice is designed for the hydraulic system to connect the rodless chamber and the rod chamber of the load simulation cylinder, thereby alleviating the pressure difference between the two chambers, especially the high pressure peak formed in the high pressure chamber.

[0011] Furthermore, the joint drive cylinder to be tested is connected to a second hydraulic control system that controls the shaft movement of the joint drive cylinder. The second hydraulic control system is a high-low pressure energy-saving hydraulic system. By designing a two-stage high- and low-pressure oil source, two different pressures can be selected for the hydraulic actuator. A high-pressure oil source is used to power the joint hydraulic cylinder in the support phase, and a low-pressure oil source is used to power the joint hydraulic cylinder in the swing phase, effectively reducing throttling losses and achieving energy saving.

[0012] Furthermore, both the first and second hydraulic control systems have pressure sensors for detecting pressure in the oil circuit.

[0013] The hydraulically driven legged robot joint control experimental platform also includes a measurement and control system, which is used to measure and receive signals from force sensors, displacement sensors and various pressure sensors, and to control the operation of the first hydraulic control system and the second hydraulic control system.

[0014] Specifically, the first hydraulic control system further includes a load simulation accumulator for maintaining a stable output oil pressure of the load simulation pump, and a relief valve for controlling the output oil pressure of the load simulation pump to not exceed the upper limit.

[0015] Specifically, the diameter of the damping orifice can be set to 0.3–2 mm.

[0016] The hydraulic control section of the joint control system test bench is designed with three types of hydraulic system circuit integration blocks, which are mounted on top of the oil tank. This facilitates signal transmission and pipeline control, reduces the length of oil pipelines, makes the overall system structure more compact, occupies less space, and also reduces friction losses in the hydraulic circuit. The circuit integration blocks are assembled as follows:

[0017] (1) The system oil source and oil circuit integration block is designed to integrate the high and low pressure oil sources of the joint control system and the oil source of the load simulation system on the oil circuit block. It is mainly responsible for the oil supply and pressure regulation of the hydraulic system, including components such as check valve, accumulator, relief valve and pressure sensor.

[0018] (2) The designed servo proportional valve group oil circuit integration block is mainly responsible for the switching of the hydraulic system, including components such as servo proportional valve and pressure sensor.

[0019] (3) The designed cartridge-type proportional directional valve group oil circuit integration block mainly includes 7 cartridge-type proportional directional valves and 2 pressure sensors.

[0020] Overall, the first oil tank, load simulation pump, servo proportional valve, load simulation accumulator, relief valve, pressure sensor for detecting pressure in the oil circuit, check valve for supplying oil to the first hydraulic control system, and cartridge proportional directional valve for controlling the direction and flow of liquid are integrated together.

[0021] Specifically, the controller design of the experimental control system for the joint control of a hydraulically driven legged robot is determined by the controlled object, including / containing a force PID controller for controlling the load simulation cylinder and a position PID controller for controlling the joint drive cylinder.

[0022] The output force of the load simulation cylinder is set to F. e The force detected by the force sensor is F. d The force PID controller will F e -F d The difference is converted into the first compensation opening U of the servo proportional valve. F ,

[0023] Set the desired position X of the joint drive rod. e The displacement detected by the displacement sensor is X. d The position PID controller will X e -X d The difference is converted into the second compensation opening u of the servo proportional valve. x ,

[0024] The compensation opening of the servo proportional valve is then the first compensation opening U. F With the second compensation opening degree u x The sum of.

[0025] When designing the controller for the load simulation cylinder, because the joint control system and the load simulation system are coupled, when the position of the control joint drive cylinder moves according to a given curve, it will affect the force control effect of the load simulation cylinder. To improve the force control effect of the load simulation system, a position control signal feedforward compensation stage is added to assist the output of the force PID controller. The force control principle block diagram of the load simulation system is as follows. Figure 10 As shown, the control signal for the servo proportional valve V4 consists of two parts: the first part is provided by the force PID controller of the load simulation system, and the second part is provided by the joint drive position PID controller. The practical effect is more stable control and reduced time lag.

[0026] This invention also provides a test method for a joint drive cylinder used in the joint control of a hydraulically driven legged robot. Using the aforementioned hydraulically driven legged robot joint control experimental platform, the test method includes the following steps:

[0027] (1) The joint drive cylinder to be tested is assembled into the hydraulically driven legged robot joint control experimental platform;

[0028] (2) The measurement and control system includes a force PID controller for controlling the load simulation cylinder and a position PID controller for controlling the joint drive cylinder.

[0029] The output force of the load simulation cylinder is set to F. e The force detected by the force sensor is F. d The force PID controller will F e -F d The difference is converted into the first compensation opening U of the servo proportional valve. F ,

[0030] Set the desired position X of the joint drive rod. e The displacement detected by the displacement sensor is X. d The position PID controller will X e -X d The difference is converted into the second compensation opening u of the servo proportional valve. x ,

[0031] The compensation opening of the servo proportional valve is then the first compensation opening U. F With the second compensation opening degree u x The sum of;

[0032] Under the control of the aforementioned controller, the force output of the load simulation cylinder is kept stable, thereby testing the response of the joint drive cylinder to different set position curves and the energy-saving efficiency of the joint control system.

[0033] Preferably, the high-low pressure energy-saving hydraulic system is a high-low pressure energy-saving hydraulic system composed of three servo proportional valves, and the servo proportional valves have hydraulic lines that are respectively connected to the rodless chamber and the rod chamber of the joint drive cylinder.

[0034] Preferably, the high-low pressure energy-saving hydraulic system is a high-low pressure energy-saving hydraulic system composed of seven cartridge proportional directional valves, wherein the cartridge proportional directional valves have hydraulic lines that are respectively connected to the rodless chamber and the rod chamber of the joint drive cylinder.

[0035] The high- and low-pressure energy-saving hydraulic system also includes a second oil tank, a high-pressure fixed displacement pump, a high-pressure servo motor, a high-pressure accumulator, a low-pressure fixed displacement pump, a low-pressure servo motor, and a low-pressure accumulator.

[0036] Two implementation methods were designed for high- and low-pressure energy-saving hydraulic systems. The first is a high- and low-pressure energy-saving hydraulic legged robot joint control system composed of three servo proportional valves. The second is a high- and low-pressure energy-saving joint control system composed of seven cartridge-type proportional directional valves. Both implementation methods can achieve energy saving by adjusting the opening and closing of the valve ports or the working state to switch the oil supply from the high- and low-pressure oil sources to the hydraulic cylinders.

[0037] The beneficial effects of this invention are:

[0038] This invention transforms self-destructive, fully physical testing into predictive research under laboratory conditions, accurately simulating complex and variable force or moment load spectra. The study utilizes a joint control test bench to conduct force loading tests in fixed positions and under varying positions, demonstrating that by incorporating position parameters of the joint control cylinder valve into the feedforward stage, the load simulation cylinder can output the expected force curve. Subsequently, step position, sinusoidal position, and high / low pressure energy-saving experiments were conducted on joint control systems based on servo proportional valves and cartridge valves, respectively, proving that using high / low pressure oil sources can save 25%-38% of energy compared to single high-pressure oil source control. Attached Figure Description

[0039] Figure 1 Design framework diagram of the joint control experimental platform of this invention;

[0040] Figure 2 This is a schematic diagram of the mechanical assembly of the joint control system test bench; where A is a schematic diagram of the mechanical assembly of the joint control system test bench, and B is a schematic diagram of the mechanical assembly of the joint control system test bench with a T-slot platform as the assembly platform for each component.

[0041] Figure 3 A simplified hydraulic principle diagram of a joint control system based on a servo proportional valve;

[0042] Figure 4A simplified hydraulic principle diagram of a joint control system based on a cartridge-type proportional directional valve;

[0043] Figure 5 A simplified diagram of the hydraulic principle of a load simulation system;

[0044] Figure 6 The following is an assembly drawing of the oil circuit integration block; where: (a) is the system oil source oil circuit integration block; (b) is the servo proportional valve group oil circuit integration block; (c) is the cartridge proportional directional valve group oil circuit integration block;

[0045] Figure 7 This is an assembly drawing of the overall hydraulic system of the test bench;

[0046] Figure 8 This is a hardware architecture diagram of the test bench and control system for the joint control system.

[0047] Figure 9 A schematic diagram of the hardware architecture of the test bench and control system for the joint control system.

[0048] Figure 10 This is a schematic diagram of the force control principle of a load simulation system.

[0049] Figure 11 This is the overall assembly drawing of the joint control system test bench;

[0050] Figure 12 The following are the knee joint trajectory response diagrams of the joint control system at 0.5Hz under two working conditions: (a) is the knee joint trajectory response of the joint control system at 0.5Hz; (b) is the knee joint load force tracking of the load simulation system at 0.5Hz; (c) is the pressure of the high and low pressure oil source system; (d) is the energy consumption of the joint control system; (e) is the control signal of each servo proportional valve under a single oil source; and (f) is the control signal of each servo proportional valve under high and low pressure oil sources.

[0051] Figure 13 The following are the 0.5Hz hip joint planning trajectory response diagrams of the joint control system under two working conditions: (a) is the 0.5Hz hip joint trajectory response of the joint control system; (b) is the 0.5Hz hip joint load force tracking of the load simulation system; (c) is the pressure of the high and low pressure oil source system; (d) is the energy consumption of the joint control system; (e) is the control signal of each servo proportional valve under a single oil source; and (f) is the control signal of each servo proportional valve under high and low pressure oil sources.

[0052] In the diagram, the markings are: 11-Load simulation cylinder, 12-Force sensor, 13-First oil tank, 14-Load simulation pump, 15-Servo proportional valve V4, 151-Damping orifice, 16-Load simulation accumulator, 17-Relief valve, 18-AC motor, 19-Check valve, 21-Second oil tank, 221-High-pressure metering pump, 231-High-pressure servo motor, 24-Accumulator, 241-High-pressure accumulator, 222-Low-pressure metering pump; 232-Low-pressure servo motor; 242-Low-pressure accumulator, 25-Servo proportional valve, 251-Servo proportional valve V1 252-Servo proportional valve V2, 253-Servo proportional valve V3, 26-Cartridge proportional directional valve, 261-Cartridge proportional directional valve K1, 262-Cartridge proportional directional valve K2, 263-Cartridge proportional directional valve K3, 264-Cartridge proportional directional valve K4, 265-Cartridge proportional directional valve K5, 266-Cartridge proportional directional valve K6, 267-Cartridge proportional directional valve K7, 27-Joint drive cylinder, 28-Displacement sensor, 3-Pressure sensor, 4-T-slot platform, 5-Filter, 6-Pressure test connector. Detailed Implementation

[0053] Example 1

[0054] 1. An experimental platform for joint control of a hydraulically driven legged robot

[0055] This invention provides a hydraulically driven legged robot joint control experimental platform for testing the joint drive cylinders used in the joint control of hydraulically driven legged robots. The experimental platform includes a load simulation cylinder 11. In use, the load simulation cylinder 11 is rigidly connected coaxially to the joint drive cylinder 27 to be tested. A force sensor 12 and a displacement sensor 28 are provided at the shaft connection between the load simulation cylinder 11 and the joint drive cylinder 27. The load simulation cylinder 11 is connected to a first hydraulic control system for controlling the shaft movement of the load simulation cylinder 11. The first hydraulic control system includes a first oil tank 13, a load simulation pump 14, and a servo proportional valve 25. The servo proportional valve 25 has hydraulic lines that are respectively connected to the rodless chamber and the rod chamber of the load simulation cylinder 11. The two hydraulic lines are connected through a damping hole 151.

[0056] More precisely, the hydraulically driven legged robot joint control test bench of this invention consists of three parts: a joint control section, a load simulation section, and a measurement and control system. The joint control section is the test object, i.e., the joint control system used in the actual robot, which drives the robot's joints. The load simulation section simulates the robot's actual working conditions, applying load to the joint control system. The test bench is equipped with a computer measurement and control system, which can control the joint control section and the load simulation section, measure their control performance and system energy consumption, and evaluate the system efficiency and performance. The design framework diagram of the hydraulically driven legged robot joint control test bench is shown below. Figure 1 As shown.

[0057] Combination Figure 1 The working principle of the joint control system test bench is as follows: The joint control system adopts position closed-loop control and is mainly composed of joint drive cylinder 27, position controller and displacement sensor 28. Its working principle is as follows: the displacement sensor 28 detects the actual position of the joint drive cylinder, transmits the position data to the controller through the data acquisition module, compares it with the desired position, obtains the deviation signal, and after processing by the controller, outputs a control signal to control the output flow of the hydraulic valve, thereby controlling the output displacement of the hydraulic cylinder; the load simulation system adopts force closed-loop control and is mainly composed of load simulation cylinder 11, force controller and force sensor. Its working principle is roughly the same as that of the joint control system, but the load simulation system and the joint control system are coupled to each other, that is, the load force of the joint drive cylinder 27 is provided by the load simulation cylinder 11, and the position and speed of the load simulation cylinder 11 are provided by the joint drive cylinder 27.

[0058] Assembly model of the mechanical part of the joint control system test bench, as shown Figure 2 As shown, the basic structure consists of two hydraulic cylinders aligned with each other. The joint drive cylinder 27 and the load simulation cylinder 11 are rigidly connected by a force sensor 12 to achieve coaxial loading. To ensure that the two hydraulic cylinders are aligned with each other as much as possible, a T-slot platform 4 is used as the assembly platform for each component. The flatness accuracy of the T-slot platform 4 can reach 16μm.

[0059] The hydraulic system of the joint control system test bench is divided into the hydraulic control part of the load simulation cylinder 11 and the hydraulic control part of the joint drive cylinder 27.

[0060] Specifically, the joint drive cylinder to be tested is connected to a second hydraulic control system that controls the shaft movement of the joint drive cylinder 27. The second hydraulic control system is a high-low pressure energy-saving hydraulic system.

[0061] The performance of hydraulically driven legged robots largely depends on the performance and efficiency of their joint control systems. Currently, most joint control systems used in legged robots employ a single-pump, multi-actuator configuration, where a single constant-pressure variable pump provides the same oil supply pressure to multiple actuators. However, due to the different leg arrangements and unique structure of legged robots, the movements and forces experienced by the joints in the support and swing phases during movement are different, leading to excess oil supply pressure in some actuator branches. This excess pressure can only be eliminated through the throttling effect of hydraulic control valves, resulting in significant energy loss. Therefore, to improve the efficiency of the joint control system, the hydraulic part of the joint drive cylinder, i.e., the second hydraulic control system, adopts a high-low pressure energy-saving hydraulic system. By designing a two-stage high- and low-pressure oil source, two different pressures can be selected for the hydraulic actuators: a high-pressure oil source is used to power the hydraulic cylinders in the support phase, while a low-pressure oil source is used to power the hydraulic cylinders in the swing phase, effectively reducing throttling losses and achieving energy conservation.

[0062] Two implementation methods were designed for high- and low-pressure energy-saving hydraulic systems. The first method consists of a high- and low-pressure energy-saving hydraulic legged robot joint control system composed of three servo proportional valves (servo proportional valves V1, V2, and V3). The second method consists of a high- and low-pressure energy-saving joint control system composed of seven cartridge proportional directional valves (cartridge proportional directional valves K1, K2, K3, K4, K5, K6, and K7). Both high- and low-pressure energy-saving hydraulic systems also include a second oil tank 21, a high-pressure fixed displacement pump 221, a high-pressure servo motor 231, a high-pressure accumulator 241, a low-pressure fixed displacement pump 222, a low-pressure servo motor 232, and a low-pressure accumulator 242. Both implementation methods can achieve energy saving by adjusting the opening and closing of valve ports or the working state to switch the oil supply from high- and low-pressure oil sources to the hydraulic cylinders. The hydraulic schematic diagram is shown below. Figure 3 and 4 As shown.

[0063] Furthermore, the first hydraulic control system and the second hydraulic control system each have a pressure sensor 3 for detecting the pressure in the oil circuit.

[0064] The hydraulic schematic diagram of the hydraulic system of the load simulation cylinder 11 is as follows: Figure 5 As shown, its oil source is a constant pressure oil source, driven by an AC motor 18 and a fixed displacement pump, with the pump outlet pressure adjusted by an overflow valve 17. The load simulation system is controlled by a servo proportional valve 25 to operate the load simulation cylinder 11. To reduce hydraulic shock phenomena in the hydraulic system and improve the force control effect of the load simulation system, a damping orifice 151 is designed for the hydraulic system. The diameter of the damping orifice 151 can be set to 0.3-2mm, connecting the rodless chamber and the rod chamber of the load simulation cylinder 11 to alleviate the pressure difference between the two chambers, especially to alleviate the high pressure peak formed in the high pressure chamber.

[0065] Based on the aforementioned hydraulic schematic diagram, the hydraulic control section of the joint control system test bench is designed with three types of hydraulic system circuit integration blocks. These integration blocks are mounted on top of the oil tank, facilitating signal transmission and pipeline control while reducing the length of the oil pipelines. This results in a more compact overall system structure, occupying less space, and also minimizing friction losses in the hydraulic circuit. The assembly diagram of the circuit integration blocks is shown below. Figure 6 As shown:

[0066] (1) The designed system oil source and oil circuit integrated block is as follows: Figure 6 As shown in (a), the high and low pressure oil sources of the joint control system and the oil source of the load simulation system are integrated on this oil circuit block, which is mainly responsible for the oil supply and pressure regulation of the hydraulic system, including components such as check valve 19, accumulator 24, relief valve 17 and pressure sensor 3 (including pressure test connector 6).

[0067] (2) The designed servo proportional valve group oil circuit integrated block is as follows: Figure 6 As shown in (b), it is mainly responsible for switching the hydraulic system, including components such as servo proportional valve 25 and pressure sensor 3 (including pressure test connector 6).

[0068] (3) The designed cartridge-type proportional directional valve manifold oil circuit integration block, such as Figure 6 As shown in (c), it mainly includes 7 cartridge-type proportional directional valves 26 and 2 pressure sensors 3.

[0069] Overall, the first oil tank 13, the load simulation pump 14, the servo proportional valve 25, the load simulation accumulator 16, the relief valve 17, the pressure sensor 3 for detecting pressure in the oil circuit, the check valve 19 for supplying oil to the first hydraulic control system, and the cartridge proportional directional valve 26 for controlling the direction and flow of the liquid are integrated together.

[0070] The overall hydraulic system assembly of the test bench is as follows Figure 7 As shown, sufficient installation space is provided between each component, and the oil ports are connected via hydraulic hoses. The oil enters the fixed-displacement pump from the oil tank via an oil filter, and then enters the oil source circuit integration block after passing through a pipeline filter. Pressure sensor 3 detects the pump outlet pressure; if the pressure exceeds the set value, the oil will flow back to the oil tank through relief valve 17. If the system pressure is normal, the oil passes through check valve 19 and accumulator 24 into the servo proportional valve 25 valve group circuit integration block, and flows into the hydraulic cylinder or back to the oil tank depending on the opening and closing of the servo proportional valve 25. By disassembling and assembling the hydraulic hoses, the oil output from the oil source circuit integration block can be connected to the cartridge-type proportional directional valve 26 valve group circuit integration block, thereby enabling testing and research on different joint control systems.

[0071] The hydraulically driven legged robot joint control experimental platform also includes a control and measurement system. The control and measurement system is used to measure and receive signals from the force sensor 12, displacement sensor 28 and each pressure sensor 3, and to control the operation of the first hydraulic control system and the second hydraulic control system.

[0072] The hardware and software architecture of the measurement and control system of the joint control system test bench is as follows: Figure 8 and 9 As shown, the hardware architecture adopts a hierarchical distributed control system structure, including a host computer, a slave computer, hydraulic control valves, various sensors and motors, etc.; the software architecture also adopts the same hierarchical distributed structure, and the entire program is written based on NI's LabVIEW 2020 software and is compatible with MATLAB language modules.

[0073] The hardware architecture mainly consists of the following two parts:

[0074] (1) Host computer: An industrial control computer is used as the host computer of the measurement and control system. It is connected to the slave computer via Ethernet. It is mainly responsible for providing a visual interactive interface for the host computer, writing and running the measurement and control software, monitoring the status of the test bench, and processing subsequent data.

[0075] (2) Lower-level machine: The NI cRIO-9040 controller is selected as the lower-level machine main controller, which is responsible for completing motion trajectory planning, motion control, control algorithm and communication in the Wi-Fi module. It is equipped with a data acquisition module NI-9220 to collect analog sensor data, including load simulation cylinder output force, joint drive cylinder output displacement, hydraulic system pressure, hydraulic cylinder two-chamber pressure, motor speed, motor power, etc.

[0076] The software architecture mainly consists of the following two parts:

[0077] (1) The first layer is completed by the host computer, which mainly controls the lower computer through the human-computer interaction interface. It is used to analyze data and transmit user control commands to the lower computer. It can control the start and stop of the test bench and realize the monitoring of the test bench status and the recording and processing of various sensor data.

[0078] (2) The second layer is implemented by the lower-level machine cRIO-9040, which is mainly responsible for data acquisition and output, and for deploying and running the overall control strategy of the test bench. The lower-level machine needs to acquire signals from pressure sensor 3, displacement sensor 28 and force sensor 12 to control the motor driver and servo proportional valve 25.

[0079] The controller design of the experimental platform for joint control of hydraulically driven legged robots is determined by the controlled object, including / containing a force PID controller for controlling the load simulation cylinder and a position PID controller for controlling the joint drive cylinder.

[0080] The output force of the load simulation cylinder is set to F. e The force detected by the force sensor is F. d The force PID controller will F e -F d The difference is converted into the first compensation opening U of the servo proportional valve. F ,

[0081] Set the desired position X of the joint drive rod. e The displacement detected by the displacement sensor is X. d The position PID controller will X e -X d The difference is converted into the second compensation opening u of the servo proportional valve. x ,

[0082] The compensation opening of the servo proportional valve is then the first compensation opening U. F With the second compensation opening degree u x The sum of.

[0083] When designing the controller for the load simulation cylinder, because the joint control system and the load simulation system are coupled, when the position of the control joint drive cylinder moves according to a given curve, it will affect the force control effect of the load simulation cylinder. To improve the force control effect of the load simulation system, a position control signal feedforward compensation stage is added to assist the output of the force PID controller. The force control principle block diagram of the load simulation system is as follows. Figure 10 As shown, the control signal for the servo proportional valve V4 consists of two parts: the first part is provided by the force PID controller of the load simulation system, and the second part is provided by the joint drive position PID controller. The practical effect is more stable control and reduced time lag.

[0084] The joint control system test bench will be mounted on a test bench frame composed of profiles and sheet metal parts. The overall three-dimensional assembly model is as follows: Figure 11 As shown.

[0085] 2. A test method for a joint drive cylinder used for joint control of a hydraulically driven legged robot.

[0086] This invention also provides a test method for a joint drive cylinder used in the joint control of a hydraulically driven legged robot. Using the aforementioned hydraulically driven legged robot joint control experimental platform, the test method includes the following steps:

[0087] (1) Assemble the joint drive cylinder to be tested into the hydraulically driven legged robot joint control experimental platform.

[0088] (2) The measurement and control system includes a force PID controller for controlling the load simulation cylinder and a position PID controller for controlling the joint drive cylinder.

[0089] The output force of the load simulation cylinder 11 is set to F. e The force detected by force sensor 12 is F. d The force PID controller will F e -F d The difference is converted into the first compensation opening U of the servo proportional valve 25. F ,

[0090] Set the desired position X of the joint drive rod. e The displacement detected by displacement sensor 28 is X. d The position PID controller will X e -X d The difference is converted into the second compensation opening u of the servo proportional valve 25. x ,

[0091] The compensation opening of the servo proportional valve 25 is the first compensation opening U. F With the second compensation opening degree u x The sum of;

[0092] Under the control of the aforementioned controller, the force output of the load simulation cylinder is kept stable, thereby testing the response of the joint drive cylinder to different set position curves and the energy-saving efficiency of the joint control system.

[0093] Example 2

[0094] High- and low-pressure energy-saving experiments were conducted on the system in Example 1. During these experiments, the power consumption of the servo motor in the joint control system was measured using a power meter to analyze the system's energy consumption. Energy consumption analysis was performed for two operating conditions: a single oil source of 15MPa and high- and low-pressure oil sources of 15MPa+9MPa, verifying the energy-saving effect of the servo proportional valve-based joint control system.

[0095] In the experiment, the joint control system provided planned trajectories for the knee and hip joints at a frequency of 0.5 Hz, respectively, and the load simulation system provided the corresponding joint load force curves. The 0.5 Hz joint trajectory position response of the joint control system is shown below. Figure 12 As shown in (a) and 13(a), the joint control system position can basically track the given signal; the 0.5Hz joint load force of the load simulation system is as follows: Figure 12 As shown in (b) and 13(b), the output force fluctuates during the oscillation phase, but it can basically simulate the actual load force of the joint and apply it to the joint control system. The pressure control effects of the high and low pressure oil sources in the joint control system are as follows: Figure 12 As shown in (c) and 13(c), the experiment shows that the system can effectively control the high and low pressure oil sources to the set values. The energy consumption curves of the joint control system are shown in Figures 13(c). Figure 12As shown in (d) and 13(d), the average power consumption of the joint control system tracking the two joint trajectories under the 15MPa single oil source condition is 1511.04W and 1119.48W, respectively; while under the 15MPa+9MPa high and low pressure oil source condition, the average power consumption of the two joint trajectories tracking the two joint trajectories is 943.44W and 830.41W, respectively. The servo proportional valve control signals for the two joint trajectories under the single oil source and high and low pressure oil source conditions are as follows: Figure 12 As shown in (e), 13(e), 12(f), and 13(f).

[0096] In summary, the joint control system underwent 0.5Hz knee and hip joint trajectory planning response tests under two operating conditions: a single oil source of 15MPa and a high and low pressure oil source of 15MPa+9MPa. The energy consumption comparison under the two operating conditions is shown in Table 1 below.

[0097] Table 1. Energy consumption comparison under two operating conditions in simulation and experiment of the joint control system based on servo proportional valve.

[0098]

[0099] Within the same cycle, using a 15MPa+9MPa high-low pressure hydraulic system, the total average power required to track the knee joint planning trajectory and hip joint planning trajectory was 943.44W and 830.41W, respectively. Compared with a 15MPa single hydraulic system, this represents energy savings of 37.56% and 25.82%, respectively. Compared to simulation, the average power consumption increased significantly in the experiment, which is related to factors such as ambient temperature, hydraulic system oil temperature, and hydraulic system leakage. The system energy consumption model established in the simulation is more ideal, but the energy-saving efficiency is basically consistent with the simulation results, verifying the effectiveness of the high-low pressure energy-saving hydraulic system design.

Claims

1. A hydraulically driven legged robot joint control experimental platform for testing joint drive cylinders used in the joint control of hydraulically driven legged robots, the experimental platform including a load simulation cylinder, wherein in use, the load simulation cylinder and the joint drive cylinder to be tested are rigidly connected coaxially and abuttingly, and a force sensor and a displacement sensor are provided at the shaft connection between the load simulation cylinder and the joint drive cylinder, characterized in that, The load simulation cylinder is connected to a first hydraulic control system that controls the shaft movement of the load simulation cylinder. The first hydraulic control system includes a first oil tank, a load simulation pump, and a servo proportional valve. The servo proportional valve has hydraulic lines that are respectively connected to the rodless chamber and the rod chamber of the load simulation cylinder, and the two hydraulic lines are connected through a damping orifice. The joint drive cylinder to be tested is connected to a second hydraulic control system that controls the shaft movement of the joint drive cylinder. The second hydraulic control system is a high-low pressure energy-saving hydraulic system. The first hydraulic control system and the second hydraulic control system each have a pressure sensor for detecting the pressure in the oil circuit. The hydraulically driven legged robot joint control experimental platform also includes a measurement and control system. The control system is used to measure and receive signals from force sensors, displacement sensors and various pressure sensors, and to control the operation of the first hydraulic control system and the second hydraulic control system. The measurement and control system includes a force PID controller for controlling the load simulation cylinder and a position PID controller for controlling the joint drive cylinder. The output force of the load simulation cylinder is set to F. e The force detected by the force sensor is F. d The force PID controller will F e -F d The difference is converted into the first compensation opening U of the servo proportional valve. F , Set the desired position X of the joint drive rod. e The displacement detected by the displacement sensor is X. d The position PID controller will X e -X d The difference is converted into the second compensation opening u of the servo proportional valve. x , The compensation opening of the servo proportional valve is then the first compensation opening U. F With the second compensation opening degree u x The sum of.

2. The hydraulically driven legged robot joint control experimental platform according to claim 1, characterized in that, The first hydraulic control system further includes a load simulation accumulator for maintaining a stable output oil pressure of the load simulation pump, and a relief valve for controlling the output oil pressure of the load simulation pump to not exceed the upper limit.

3. The hydraulically driven legged robot joint control experimental platform according to claim 1, characterized in that, The diameter of the damping orifice is 0.3~2mm.

4. The hydraulically driven legged robot joint control experimental platform according to claim 2, characterized in that, The first oil tank, load simulation pump, servo proportional valve, load simulation accumulator, relief valve, pressure sensor for detecting pressure in the oil circuit, check valve for supplying oil to the first hydraulic control system, and cartridge proportional directional valve for controlling the direction and flow of liquid are integrated together.

5. A test method for a joint drive cylinder used for joint control of a hydraulically driven legged robot, characterized in that, Using the hydraulically driven legged robot joint control experimental platform as described in claim 1, the testing method includes the following steps: (1) The joint drive cylinder to be tested is assembled into the hydraulically driven legged robot joint control experimental platform; (2) The measurement and control system includes a force PID controller for controlling the load simulation cylinder and a position PID controller for controlling the joint drive cylinder. The output force of the load simulation cylinder is set to F. e The force detected by the force sensor is F. d The force PID controller will F e -F d The difference is converted into the first compensation opening U of the servo proportional valve. F , Set the desired position X of the joint drive rod. e The displacement detected by the displacement sensor is X. d The position PID controller will X e -X d The difference is converted into the second compensation opening u of the servo proportional valve. x , The compensation opening of the servo proportional valve is then the first compensation opening U. F With the second compensation opening degree u x The sum of; The test examines the response of the joint drive cylinder to different position curves and the energy efficiency of using the second hydraulic control system.

6. The test method for the joint drive cylinder for joint control of a hydraulically driven legged robot according to claim 5, characterized in that, The high- and low-pressure energy-saving hydraulic system is a high- and low-pressure energy-saving hydraulic system composed of three servo proportional valves. The servo proportional valves have hydraulic lines that are respectively connected to the rodless chamber and the rod chamber of the joint drive cylinder.

7. The test method for the joint drive cylinder for joint control of a hydraulically driven legged robot according to claim 5, characterized in that, The high- and low-pressure energy-saving hydraulic system is a high- and low-pressure energy-saving hydraulic system composed of seven cartridge-type proportional directional valves. Each cartridge-type proportional directional valve has a hydraulic pipeline that is connected to the rodless chamber and the rod chamber of the joint drive cylinder, respectively.

Images