QNX-based Development Of Distributed Control System For Hydraulic Quadruped Robot

The quadrupedal mammals in nature can access almost any place on the land surface with their legs and feet,who have the advantages of strong terrain adaptability,high load-bearing capacity and highly flexible mobility.Therefore,the quadruped bionic robot imitating quadrupedal mammal has become a research hotspot in the field of mobile robots.The quadruped robot control system,as the core part of the robot,is responsible for tasks such as executing control commands,performing joint-driven servo control,monitoring robot operation status,and dynamic stability control under external disturbances.And the real-time,software and hardware system reliability of this part plays a key role in the overall performance of the robot system.According to the requirements of real-time performance,resistance to common mode interference and high reliability of the quadruped robot SCalf developed by Shandong University,a hierarchical distributed architecture is adopted to design the robot control system.The main research contents are as follows:(1)The overall design of the control system.Based on the analysis of the mechanism composition,joint driven method,airborne energy and movement modes of the hydraulically actuated quadruped robot system,the design requirements of the robot control system are proposed.Then according to the requirements of the control system,firstly,the dynamics of the robot system is divided into the overall dynamic model and the single-leg dynamic model.And the core controller and the single-leg servo controller are used for the calculation and control respectively to improve the real-time performance of the model solution and computational efficiency.Secondly,the use of dual CAN bus communication methods separates transmission of robotic power system control and motion control information to increase communication bandwidth.By dividing the control system into core control layer,coordination communication layer and servo drive layer,a highly reliable hierarchical distributed control system hardware architecture is designed,and detailed design of each layer is carried out.(2)The hardware implementation of the control system.According to the requirements of the control task,the main device is selected first under the overall framework of the control system.The core controller with the ADLINK CM920 as the CPU and the Connect CANpro/104-plus Opto as the CAN card is determined.Different matching circuits were designed for different functional requirements.Finally,the reliability of the control system is designed to ensure the stability of the control system(3)Software design of the control system.The IDE Monmentics development environment was built based on the QNX real-time operating system.According to the framework design of the control system,the threads of the core control layer were first allocated and the main thread program was designed.Secondly,software was designed for different communication methods of the communication coordination layer and a CAN communication protocol was established.Then according to the data acquisition and output requirements,the A/D acquisition and D/A output of the servo execution layer are designed.Finally,the upper computer operation interface is designed to facilitate the robot's operation control and running status monitoring.(4)Experimental verification.A verification experiment of the A/D data acquisition module and the D/A output module,a single-cylinder servo control experiment,a CAN communication experiment,and a complete machine experiment were designed.The data acquisition and output of the control system and the following performance of the single-cylinder servo control,the CAN communication speed and the overall performance of the robot were respectively tested.The experimental results show that the system meets the new control requirements and can carry out experimental verification of relevant algorithms on quadruped robots.