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Hydraulic actuated quadruped robot similar to BigDog has two primary performance requirements, load capacity and walking speed, so that it is necessary to balance joint torque and joint velocity when designing the dimension of single leg and controlling its motion. On the one hand, because there are three joints per leg on sagittal plane, it is nec...
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... The output signals of other joints affect the input of one joint, and at the same time, the output of one joint affects the input signals of other joints. 3,4 Therefore, there is a coupling phenomenon among robot joints. This phenomenon introduces many difficulties to the control method of robot joint control; thus, determining the strategies among robot joints has become one of the most difficult problems. ...
To enhance the joint control performance in hydraulic quadruped robots, active disturbance rejection control was used in the leg joint controller design of a hydraulic quadruped robot in combination with the self-growing lévy-flight salp swarm algorithm in this paper. First, the robot-leg structure of the hydraulic system model was built to analyze system operation details in terms of the mathematical construction. Second, the self-growing lévy-flight salp swarm algorithm was introduced. Then, the active disturbance rejection control parameters required were defined based on the composition and principle of the third-order active disturbance rejection control model. Third, the system evaluation function ITSE was selected, and the parameter tuning problem was converted into an algorithm optimization problem. Finally, the joint system of the hydraulic quadruped robot was taken as the research object, the self-growing lévy-flight salp swarm algorithm was added to the active disturbance rejection control to tune parameters, and this paper compared three different algorithms in the same environments to show the good control ability of the proposed method. To comprehensively show the performances of robot joint systems controlled by the proposed controller, the temporal response results, the frequency response results, the sawtooth response results, the ramp response, and the random response were displayed. All results reveal the effectiveness and excellent performance of the proposed controller in joint systems of a hydraulic quadruped robot.
... Where, ESC is expressed as the abbreviation of Electro-Servo Cylinder. According to the related research [23][24][25][26], the transfer function expression of the single-cylinder servo system with an electro-hydraulic position is derived according to Eq. (3). ...
An Electro-Hydraulic Servo (EHS) Four-Footed Heavy-Duty (FFHD) robot is designed and developed in this work. An integration layout cylinder design scheme for the non-lightweight EHS four-footed robot with high loads and hip joint torques is proposed, and a mathematical element analysis model for a parallel EHS cylinder system is derived. Multiple inherent characteristics of the parallel-executed cylinder integration system model are then further explored. Based on the controllable functional requirements of interconnected joints and the influence reduction in internal force coupling, a force/position hybrid control scheme for the parallel-executed cylinder is determined, and the force/position signal module design unit is used to solve the force/position hybrid control in reverse. The implementation process of magnetic flux compensation and speed compensation is discussed in detail, considering the inherent requirements of the EHS-executed cylinder force control unit module. A compliant controller is then applied to the EHS-executed cylinder force unit module, and the proportional integral derivative (PID) controller is determined in the EHS-executed cylinder position control unit module. The compound control strategy proposed in this paper is verified on a parallel EHS platform. The experimental verification results reveal that the values of position/force attenuation amplitude and lag phase are no greater than 10.0% and 20°, respectively. The feasibility of the interconnected implementation of the proposed hybrid control scheme is then analyzed. The conclusions obtained in this research provide relevant insights for the application of FFHD robot control systems.
... To avoid the interference of asynchronous motion, the attention will be paid to the position of a servo actuator with electro-hydraulic in its control mode. According to the related research in the reference [23][24][25][26], as shown in Eq. (1), the transfer function expression of the single-cylinder servo system with an electro-hydraulic position should be derived: ...
In this research subtopic, an electro-hydraulic servo four-legged heavy load (FLHL) robot has been designed and developed. This paper proposes an integration layout cylinder design scheme for a non-lightweight hydraulic servo four-legged robot with high loads and torques of hip joint, and derives the mathematical element analysis model for a parallel hydraulic servo cylinder system. The multiple inherent characteristics of the parallel-executed cylinder integration system model are further explored. Based on the controllable functional requirements of interconnected joints and weakening the influence of internal force coupling, a design idea of force/position hybrid control scheme for the parallel-executed cylinder is determined, and then the force/position signal module design unit is used to reversely solve the force/position hybrid control. Considering the inherent requirements of the servo-executed cylinder force control unit module, the implementation process of magnetic flux compensation and speed compensation is discussed in detail. The minimum amplitude controller is applied to the servo-executed cylinder force unit module, and the proportional integrated controller has been determined in the servo-executed cylinder position control unit module. A compound control strategy proposed in this paper is verified on a parallel hydraulic servo platform. The experimental verification results reveal that the values of position/force attenuation amplitude and lag phase are not greater than 9 % and 18°, respectively. In addition, the feasibility of the interconnected implementation of the hybrid control scheme proposed in this paper is further deepened. The effective conclusion of this research will be accepted in the application field of FLHL robot control system.
... On the basis of the above analysis, a new kind of optimization criterion consisting of support phase and flight (swing) phase is proposed in our previous paper and converted onto angular acceleration level based on ZNN. A feasible distribution of the joint torques and angular velocity is obtained according to continuous mid-value CLVI-PDNN, but the algorithm used in our previous paper has a drawback, i.e., hard to real-time application because of too large computation cost [31]. ...
... In our previous paper [31] two kinds of neural network are proposed based on LVI-PDNN, i.e., CLVI-PDNN and midvalue CLVI-PDNN. CLVI-PDNN improves the drawback of open-loop LVI-PDNN such as divergency of the optimized results from the desired value. ...
... As analyzed in our previous paper [31], the mid-value CLVI-PDNN just compromise between the inequality and equality constrains. That is to say, the output of the QP solver maintains in motion range of the joints ensuring a feasible rather than optimal solution on condition that the error between the desired and the optimized trajectory is not enough to destroy normal motion control. ...
The two most important performance indicators of quadruped robot are load capacity and walking speed, and these performance indicators of the whole robot finally reflect on the joint torques and angular velocities. To satisfy different requirements of walking speed and load capacity when quadruped robots implement different tasks, the joint torques and angular velocities need to be balanced with physical constraints of the joints. A single leg with redundant DOF (degree of freedom) could optimize the distribution of joint torques or angular velocities based on different performance requirements. This paper presents a kind of new recurrent neural networks taking joint torques and angular velocities simultaneously into consideration and proposes mid-value CLVI-PDNN to achieve the optimal joint torques and angular velocities with physical constraints of the mechanism as described in our previous paper. Because the continuous mid-value CLVI-PDNN has difficulty in real-time operation because of too much calculation workload, two kinds of methods are proposed to discretize the mid-value CLVI-PDNN for application on computer or digital circuit. The simulation results demonstrate the efficacy of the algorithm proposed in this paper.
... They built a velocity controller based on energy control and vestibular reflexes. Zhang et al. [20] optimized the distribution of joint torques and velocity of a redundant single leg with joint physical limitations. The modified optimization criterion combining joint torques with angular velocity was proposed. ...
The articulated rotating speed is one of the important parameters to determine the drive devices and actuating devices of joints for legged robots. Compared with the small-scale multi81legged robots, the range of output speed of the joint should be as accurate as possible for the large81load81ratio multi81legged robots.To reasonably select the devices of joints, the maximum walking speed method is proposed to quickly and accurately obtain the range of articulated rotating speed by taking an electrically driven large-load-ratio six-legged robot as an example. To prove the rapidity, accuracy, and conciseness of the maximum walking speed method, the analyses of the forward kinematics and inverse kinematics of robot are implemented based on the Denavit–Hartenberg (D–H) method. However, only one range of articulated rotating speed is effectively confirmed in a single leg. Through rotating one of joints to achieve the maximum speed index of robot, the maximum walking speed method is employed to establish the mathematical relationships between the articulated rotating angles and the maximum walking speed index of robot. The ranges of the output speeds of all joints are accurately obtained. The simulation verification and walking experiments of prototype are respectively carried out. The results of the simulation and walking experiments show that the maximum walking speed method is reasonable and effective in calculating the range of articulated rotating speed. The proposed method in this article can be reliably applied to the development of large-load-ratio multi-legged robots.
The hydraulic joint is the key driving component of a robot. To reduce the joint size of the hydraulic robot, and improve the control accuracy and dynamic response performance, this paper proposes a novel joint structure and control method of a ball double-screw hydraulic robot. Using ball and circular arc spiral groove transmission, the hydraulic joint has a small transmission friction coefficient, compact overall structure and higher transmission accuracy. Aiming to resolve the problems of low control accuracy and motion instability caused by temperature drift in valve-controlled hydraulic systems, the high-precision joint control method based on adaptive fuzzy control compensation is used to improve the control accuracy and stability. The static and dynamic characteristics of the designed hydraulic joint are analyzed by simulation. A test platform was built, and the physical prototype of the hydraulic joint underwent static testing, dynamic control, amplitude frequency response and trajectory tracking tests. The experimental results were similar to the simulation results. The ball double-screw hydraulic robot joint has the characteristics of low starting pressure, high energy density, fast dynamic response, small amplitude frequency attenuation and high control accuracy. The starting pressure is 0.5 MPa, maximum swing frequency is 3 Hz, positioning accuracy is ± 0.03°, tracking accuracy is ± 3.9° and maximum angular velocity at 10 MPa is about 7.6 rad/s, which is close to the angular velocity of the actual human joint. © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Autonomous mobile robots are being used for disinfection tasks as an alternative to reduce the exposure of cleaning personnel. In this article a new mobile robot manipulator is introduced for disinfection, by means of a fog generator. The robot consists of a differential drive platform and a two degrees of freedom (DoF) arm which is used to handle a fogging nozzle. For this nozzle a coverage path and a trajectory in the configuration space of the robot needs to be planned. Thus, this work presents a solution to the trajectory planning problem for kinematic control of a predefined end effector path of our disinfection robot, based on the application of a Non Dominated Sorting Genetic Algorithm (NSGA-II), for optimization of energy and smoothness functions for the joint motions. It is assumed that in a previous stage the coverage path planning (CPP) problem was solved. However, a discussion is also presented on the different methods that could be used for CPP.
In the article, a heavy-duty quadruped robot was designed. A parallel cylinder transmission scheme for the heavy load torque of the hip joint of heavy-duty hydraulic quadruped robot is proposed, the mathematical model of the parallel cylinder system is derived, the model characteristics of the parallel cylinder system are analyzed, the characteristics of internal force and joint control of parallel cylinders are considered, the force/position hybrid control of parallel cylinder is proposed to eliminate the internal forces and realize the requirement of joint control and the force/position control is decoupled by the design of the force and position signal. According to the characteristics of the servo cylinder force control model, the flow compensation and speed compensation are introduced, the minimum control synthesis controller is used to control the servo cylinder force and the proportional integral controller is applied to control the position of servo cylinder. The compound control strategy is analyzed on the table of parallel cylinder, and the experimental results show that the amplitude attenuation and phase lag of position and force are less than 10% and 18°, respectively, and the efficiency of the proposed control strategy is verified. The research results of this article will be widely used in many fields of robot control in the future.
