Pei Zhongcai

Adaptive Controller for 6-DOF Parallel Robot Using T-S Fuzzy Inference

6-DOF parallel robot always appears in the form of Stewart platform. It has been widely used in industry for the benefits such as strong structural stiffness, high movement accuracy and so on. Space docking technology makes higher requirements of motion accuracy and dynamic performance to the control method on 6-DOF parallel robot. In this paper, a hydraulic 6-DOF parallel robot was used to simulate the docking process. Based on this point, this paper gave a thorough study on the design of an adaptive controller to eliminate the asymmetric of controlled plant and uncertain load force interference. Takagi-Sugeno (T-S) fuzzy inference model was used to build the fuzzy adaptive controller. With T-S model, the controller directly imposes adaptive control signal on the plant to make sure that the output of plant could track the reference model output. The controller has simple structure and is easy to implement. Experiment results show that the controller can eliminate asymmetric and achieve good dynamic performance, and has good robustness to load interference.

Research of the servo pump's electrically driven variable displacement mechanism

In this paper, an electrically driven variable displacement servo pump was designed to meet the requirement of dual-variable control in integrated electro-hydrostatic-actuator. The driving force of variable displacement mechanism of the servo pump was analyzed, and the mathematical model was created. A DC servo motor was selected as the executive unit of the variable displacement mechanism, the structure of the mechanism that drives the swashplate and the digital controller using digital signal processor (DSP) was designed.

Fuzzy PID control of Stewart platform

Stewart platform equipped with asymmetric hydraulic cylinder controlled by symmetric valve has features such as nonlinearity, time variance and strong interference, which lead to various difficulties in control process. Fuzzy control algorithm is an in-time regulating parameters algorithm, which has the ability to emulate the behavior of a human operator. Fuzzy logic control shows its priority in real-time nonlinear system control. This paper represents a detailed way of hydraulic servo system modeling. A control algorithm based on fuzzy logic control algorithm combined with PID control algorithm is established. Computer simulations and experiments show that the position servo system can obtain a satisfactory performance using fuzzy PID controller.

Trajectory planning and mechanic's analysis of lower limb rehabilitation robot

A new rehabilitation robot was designed. The robot included a suspension mechanism, a drive unit, and an adjustment mechanism. Additionally, innovative weight loss mechanism increased the dynamical device so that it could be used with patients of varying lower extremity muscle strengths. The relationship of hip and knee angles with height, step length, and gait cycle was studied. It was developed to generate different trajectories for different patients. Kinematics and dynamics were studied to lay the foundation for control.

Structure analysis of hydraulic jumping robot

This paper focuses on the design of a new hydraulic jumping robot. This robot platform has four legs and can execute some highly dynamic tasks, like walking, trotting, galloping and especially jumping. Hydraulic actuators have been chosen to drive active joints in order to meet the performance requirements of the robot for torque, compactness, velocity, impact resistance and control bandwidth. The main research work aims at the design of robot structure, descriptions of geometry relationships, parameters selection and implementation of jumping movement. The evaluations and analyses of the robot have finished based on the simulation results using AMESim software. These simulation analyses will greatly promote the later research work.

Theoretical analysis of surplus torque in electro-hydraulic load simulator

There is mutual interference between force system and steering gear system when the electro-hydraulic load simulator is working. This interference causes large surplus torque in the loading system, which affects the loading accuracy and the dynamic performance greatly. In this paper, in-depth theoretical analysis of the electro-hydraulic load simulator has been presented, the mathematical model of surplus torque has been built up, all kinds of factors which affect the surplus torque have been discussed, simulation and experiments have been made to testify the results. It can be concluded that the velocity disturbance from steering gear acting on the loading system is the key factor which brings about the surplus torque. Proper selection of load systems structural parameters, such as load stiffness, motor displacement and effective volume, is crucial to the high performance electro-hydraulic load simulators implementation.

Strategies for shooting based on fuzzy logic and artificial potential field in robot soccer systems

Goal scoring is the main objective of the robot soccer game. This paper presents strategies of shooting for robot soccer systems. Using an algorithm based on fuzzy logic, we employ an arbiter to identify the most suitable shooter in a soccer team when attacking. We also propose an algorithm based on artificial potential field to plan an appropriate path for the chosen shooter. In the games, the team based on these strategies showed significantly good performances in shooting action.

Research on Gait and Control of Bionic Hexapod Robot

With the development of science and technology and the improvement of software and hardware, many scientists have focused on the research of robots and bionic robot technology is more and more popular. At first, in the military, the wheeled and tracked robots have been widely used, but with the continuous expansion of the applied scope of human robot, in complex environment, these two types of robots have been unable to meet the demand. Compared with the wheeled and tracked robot, legged robot has obvious advantages in rugged environment. Compared with bipedal and quadrupedal robot, the hexapod robot has redundant structure and its carrying capacity and stability are also improved. Hence, the development of hexapod robot has become a hot spot. In this paper, the structure and the prototype of the hexapod robot are designed. Using the bionic principle, the six legs are distributed on both sides of the body, each leg has three degrees of freedom, which ensure the robots perfect movement ability. Through the comparison of several kinds of gait, the gait trajectory planning and time sequence control of six feet are summarized. In this paper, we mainly study the gait control of the hexapod robot and the redundancy of the leg. The basic purpose is to achieve the control of hexapod robots six legs in accordance with the expected speed and the forward direction so that the robot can walk stably and quickly. Moreover, when one to three legs are out of order, adjust the angle between the remaining legs and adjust the center of gravity to keep it stable, it can still walk steadily.

Adaptive motion cueing algorithm based on fuzzy tuning for improving human sensation

As one of the key technologies of flight simulator, motion cueing algorithm (MCA) plays a great role in regenerating realistic motion and the similar human perception within physical limitations. Although it is the most popular MCAs, classic washout algorithm has some drawbacks, including distortion of the original signal, false cue motions, poor usage of the workspace and wrong human sensation. In order to overcome these problems and minimize human sensation error between the actual flight and simulator while exploiting the platform more efficiently within the motion constraints, this paper proposed a new method which adopt signal error compensators based on fuzzy logic online tuning. And the fuzzy tuning logic controller based on displacement, workspace limitation and the sensed specific force error. The proposed method also contains a non-linear scaling factor to adjust the amplitude of the input signal and uses partial range scaling of the tilt rate limiter to overcome the discontinuous movement. After simulating and analyzing, it shows the superiority of the proposed MCA as it decreases human sensation error to meet high fidelity and exploit platform workspace more efficiently within physical limitations to deliver realistic motion.

Sliding mode control for electrohydrostatic actuator

Electrohydrostatic actuator (EHA) is a new actuator for next generation aircraft actuation system. This actuator is essentially a nonlinear system; response speed and accuracy are the main consideration. We use sliding mode control for this nonlinear system in this paper. The variable structure filter (VSF) is introduced to obtain the unmeasured states. Derivation of the VSF gain based on the reaching law is presented in this paper. To improve the response speed and accuracy, a nonlinear function is introduced to construct the nonlinear sliding surface using the estimated states generated by VSF. Simulation results show that low settling time and quick response are obtained by using the nonlinear sliding surface.