Liangwen Wang

Motion Error Compensation of Multi-legged Walking Robots

Existing errors in the structure and kinematic parameters of multi-legged walking robots, the motion trajectory of robot will diverge from the ideal sports requirements in movement. Since the existing error compensation is usually used for control compensation of manipulator arm, the error compensation of multi-legged robots has seldom been explored. In order to reduce the kinematic error of robots, a motion error compensation method based on the feedforward for multi-legged mobile robots is proposed to improve motion precision of a mobile robot. The locus error of a robot body is measured, when robot moves along a given track. Error of driven joint variables is obtained by error calculation model in terms of the locus error of robot body. Error value is used to compensate driven joint variables and modify control model of robot, which can drive the robots following control model modified. The model of the relation between robot’s locus errors and kinematic variables errors is set up to achieve the kinematic error compensation. On the basis of the inverse kinematics of a multi-legged walking robot, the relation between error of the motion trajectory and driven joint variables of robots is discussed. Moreover, the equation set is obtained, which expresses relation among error of driven joint variables, structure parameters and error of robot’s locus. Take MiniQuad as an example, when the robot MiniQuad moves following beeline tread, motion error compensation is studied. The actual locus errors of the robot body are measured before and after compensation in the test. According to the test, variations of the actual coordinate value of the robot centroid in x-direction and z-direction are reduced more than one time. The kinematic errors of robot body are reduced effectively by the use of the motion error compensation method based on the feedforward.

Inverse kinematics analysis of multi-legged walking robots based on hand-foot-integration mechanism

Development of integrated hand-foot function is the inevitable choice for the practical application of multi-legged robots. In this paper, a new type of robot which has the structure of multi-legged walking robot based on hand-foot-integration is introduced. Kinematics relations between walking and grasping states of robot are described. The inverse kinematic is analysed in details. Firstly, the parameters expression of standing state of robot is derived from the constrain of the robot structure. Secondly, the kinematics relation of serial manipulator with grasping function is researched. Finally, the inverse kinematics of robot in grasping object is obtained. The relevant formula is deduced in this paper, and the formula expression is given. The analysis process is last verified through a numerical example. The model can be used for motion control of robot.

Error Analysis Modeling of Multi-legged Walking Robots

Determining precisely the motion of robot body is of great significance to the location and control of mobile robots. If the positions of each foothold and the driven joint variables are inaccurate, actual posture of the robot is likely to deviate from its required position. If the expected accuracy of robot’s locus is given, the robot can walk under expectation by controlling the accuracy of driven joints. On the basis of the inverse kinematics of a multi-legged walking robot, in this paper, the relation between accuracy of robot’s locus and errors of driven joint variables is discussed. The error expressions of a robot were obtained according to its structure and motion constraints, which include the motion errors of footholds in body and hip coordinates, the motion error of orientation matrix, and the error of driven joint variables. The equation set was obtained, which expresses relation among error of driven joint variables, structure parameters and error of robot’s locus. The formulae are derived in this paper. The analysis process is verified through a numerical example. This analysis model is the base of error compensation in controlling walking robots.

Improved forward kinematic analysis of a reptile-like four-legged walking robot using a novel dimensionality-reduction method:

A new forward kinematic analysis is proposed to describe the motion of a reptile-like four-legged walking robot using a new dimensionality-reduction method. The three standing legs (assuming one leg is swinging) contain nine driven joints. Only six of these joints, however, are independently driven joints. The remaining joints are redundant driven joints. Finding the redundant driven joint angles has been a key problem in improved forward kinematic analysis of a reptile-like forward kinematic analysis. Solving the associated high-order equation, which is derived using the analytic method, is problematic and slow. In this paper, we use a new dimensionality reduction method to solve this problem. First, we deduced the formulas for the redundant driven joint angles. Then, one of the formulas is transformed to take into account the constraint condition. We then use iteration to find solutions for the remaining equations that satisfy the constraint condition. With the help of MATLAB, a solving system for the forward kinematic analysis of this robot is introduced. Our results show two improvements over the conventional method: shorter computation time and higher precision.

A robot ultrasonic mapping method based on the gray system theory

A robot mapping algorithm based on the gray system theory is described in this paper. The ultrasonic error model is established according to the sound wave transmission character and a gray value is defined to express the sensor data uncertainty. In this algorithm, several continuous sonar data are fused based on the gray system fusion theory in order to update the gray value of the map grid. A grid neighborhood searching method is proposed to judge the robot accessible position, plan the feasible path for the complete map of the whole environment. The validity and accuracy are proved in the real office environment.

Accuracy Synthesis of a 3-R2H2S Parallel Robot Based on Rigid-Flexible Coupling Mode

On the basis of accuracy analysis of rigid-flexible coupling model of 3-R2H2S parallel robot, the pose error analysis and synthesis is studied systematically in this paper. In terms of rigid analysis, the accuracy mathematical model of 3-R2H2S parallel robot is established by the differential theory based on the inverse solution. The independent and equal effect principle of error is applied to the accuracy synthesis of the robot. Through the computer simulation, the distribution of structure parameter errors is analyzed according to the allowable range of pose error. The simulation results show the active arm error has the most remarkable influence on the pose error of the parallel robot. As for flexible analysis, the rigid-flexible coupling model of 3-R2H2S is established by the software ADAMS and ANSYS. The simulation results of rigid-flexible coupling model show the elastic deformation of the fore arms plays a major role in the robot pose error. The methods proposed in this paper have provided theoretical basis for accuracy synthesis for parallel robot of this type.

Research of Course Teaching System Reform with the Characteristic of Light Mechanism Design

This paper focuses on the course teaching system reform with light mechanism design. In the training process of light mechanism design, the ability of solving practical problems and improvement of their scientific interest need to be enhanced and cultivated. Thus the existing curriculum system should be reformed. Take the course of mechanism design in light industrial mechanics department for example. Firstly, research the teaching material about mechanism design with light mechanism design and add them to teaching material and multimedia courseware. Secondly refer to and follow the famous magazine and elaborate multimedia courseware with practical light mechanism. Then, introduce the modern design and teaching methods (CAD, CAE) into the light mechanism analysis. Finally, guide students to participate in scientific research activities, and strengthen the fusion penetration of mechanism design knowledge. Using these, the ability of using Solidworks and Ansys to solve practical problems and students scientific interest can be enhanced and improved.

Control system design for multi-legged robot with hand-fused foot

In this paper, a distributed motion control system is designed and achieved for the modular multi-legged robot with hand-fused foot based on CANopen network. A communication network is built among modules and joints through CANopen network. Controllers and encoders are used to achieve closed-loop control for each joint. The system has completed real-time multi-jointed linkage. Moreover, experimental results have proved the reliability and validity of this control systems hardware and software.

Mechanism configuration design of multi-legged walking robots based on hand-foot-integrated function

At present, most of multi-legged walking robots are still facing problems such as single function and maintainability. Walking robots are usually as a simple mobile platform. In order to expanding the application of the robot, the modular multi-legged walking robot based on hand-foot-integrated function is described in this paper. The robot not only can complete the walk but also can grasp the object by taking advantage of the legs griping function. In this paper, the design concept and structure of such robot are introduced in details. The amount, the shape and the DOF of finesse, the selection of drive mode and transmission mechanism are discussed. Two typical hand-foot-integrated structures which can finish this function are introduced, it contains clamp structures robot and underactuated articulated structures robot. Design issues of two typical structures are discussed.