Xinjie Wang

Mechanism Design and Gait Experiment of an Amphibian Robotic Turtle

In this paper we describe the design of a new bio-inspired amphibian robot with high environmental adaptability. The robot, called MiniTurtle-I, can transform terrestrial and aquatic locomotion configurations through a new variable topology mechanism (Leg-Flipper). Based on the modular design philosophy, four rotatory joint modules (Joints I–IV) constitute a Leg-Flipper module. Variable topology structure transformation of Leg-Flipper by actuation redundancy enables the robot to achieve a variety of locomotion. Our motivation is to provide another solution to achieve amphibious movement both easily and efficiently. A prototype of MiniTurtle-I is built to exam the configuration transformations. Terrestrial, aquatic and semiaquatic gait experiments are performed to verify the locomotion functions of the MiniTurtle-I.

Forward Kinematics Analysis and 3-Dimmision Gait Simulation of a MiniQuad Walking Robot

Kinematics analysis is essential for robotic design and control. The forward kinematics of a multilegged walking robot is very complicated due to its complex mechanism and redundant actuation. In this paper, the forward kinematics of reptile-like multilegged robots is analyzed by considering the basic walking pattern with three supporting legs. The redundant joint variables are first derived and expressed in terms of the independent joint variables. Based on the redundant actuation analysis, the forward position, velocity, and acceleration are derived. The resultant formulas are verified through a numerical example and a simulation on a multilegged walking robot MiniQuad-I.

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.

Control System of a Modular and Reconfigurable Multilegged Robot

Comparing to other robot systems, the modular reconfigurable walking robot has good adaptability to complex terrain, high flexibility and high extensibility. A distributed hierarchical control system of a modular walking robot is proposed and the prototype is built in this paper. The control system is composed of a PC-based computer, a body-level controller and several base-level controllers. The expansive software architecture featuring three-level hierarchy is proposed and offers support to the modularity of the control system. By the simulation and experiments, it is proved that the robot has the walking, object packing and reconfigurable abilities, and each joint module has the plug and play function.

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.

Computer Aided Geometric Method of Forward Kinematics Analysis of Multi-Legged Walking Robots

The high order equation causing by analytic method in multi-legged robot forward kinematics analysis may have imaginary root, repeated root, extraneous root or even lost solution. A system based on the theory of computer aided geometric method is proposed. Consideration with the internal structural constraint relations of multi-legged walking robots, the solidworks model was constructed and Visual Basic develop platform was adopted to fulfill the secondary development of solidworks. A system of forward kinematics analysis of multi-legged walking robots is established. The example validates that the system is simple and effective for all reptiles-like quadruped walking robot.

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.

Configuration and Motion Simulation of Multi-Legged Walking Robots with Hand-Food-Integrated Mechanism Arm

The paper introduces the configuration of a multi-legged walking robot with hand-food-integrated mechanism arm. In order to study the kinematics and the dynamics of the robot, three-dimensional entity model of the multi-legged walking robot is built up in solid-works based on inner relation of different simulation softwares. And then the model is leaded in ADAMS to simulate the dynamics and the kinematics of the robot. The paper describes the corresponding process. As an example, the robot ZQROT-1 walking along straight line is investigated. Dynamic parameters of the robot are obtained and analyzed by using ADAMS. The results can be used to optimize the robot structure and to determine its characteristic parameter. The methods and the thoughts of the paper can be referenced to solve similar problem in some aspects.