Yuechao Wang

An LMI approach to stability of systems with severe time-delay

This note describes the stability problems of uncertain systems with arbitrarily time-varying and severe time-delay. Using new Lyapunov-Krasovskii functionals, less conservative stability conditions are obtained for such systems. The results are illustrated using the numerical examples based on simple linear matrix inequalities.

Analysis of stairs-climbing ability for a tracked reconfigurable modular robot

Stairs-climbing ability is the crucial performance of mobile robot for urban environment mission such as urban search and rescue or urban reconnaissance. The track type mobile mechanism has been widely applied for its advantages such as high stability, easy to control, low terrain pressure, and continuous drive. Stairs-climbing is a complicated process for a tracked mobile robot under kinematics and dynamics constraints. In this paper, the stairs-climbing process has been divided into riser climbing, riser crossing, and nose line climbing. During each climbing process, robots mobility has been analyzed for its kinematics and dynamics factor. The track velocity and accelerations influences on riser climbing have been analyzed. And the semiempirical design method of the track grouser and the module length has been provided in riser crossing and nose line climbing correspondingly. Finally, stairs-climbing experiments have been made on the two-module robot in line type, and three-module robot in line type and in triangle type respectively.

Serpentine locomotion of a snake-like robot controlled by cyclic inhibitory CPG model

Based on the structure of both biological snakes and snake-like robots and their rhythm locomotion, the theory of the cyclic inhibitory CPG is adopted as a control method to construct a neuron network model of the snake-like robot. The relation between the CPG parameters and the serpentine locomotion of the snake-like robot is defined in this paper. The validity of the serpentine locomotion controlled by the CPG model is verified through a snake-like robot model. The modulating methods of the CPG parameters are brought forward and simulated to realize the required turn motion and the reconfiguration. Moreover, we present that real snake-like robot can successfully exhibit serpentine locomotion by using controller output of the proposed architecture. Finally, the aspects of future researches are discussed.

Analysis of traveling wave locomotion of snake robot

The mechanism of traveling wave locomotion of a snake robot was analyzed in the paper. Its kinematics model was founded and a modified control strategy was conducted in a reconfigurable snake robot. The results shows that in one period the locomotion can be divided into four phases according to the number of joints contacting with the supporting plane, and the resultant force of the friction forces on contacting joints generates locomotion. The modified control method can form smoother body curve and generate the accelerated or decelerated locomotion. Experimental results show that using traveling wave locomotion the robot is able to go forward and backward, and turn around, especially can move in a narrow site and some partial unstructured environments. The maximum linear velocity that can obtain is 0.04 m/s, the slope of the inclined plane that can be climbed is 20/spl deg/ on a carpet, the maximum wideness of gap that can be crossed is 0.14 m, and the minimum diameter of the pipe that can be gone through is 0.06 m.

Locomotion control of a novel snake-like robot

It is essential to design a joint mechanism for snake-like robots to exhibit more mobility, no singularity and powerful actuation for many applications. By adding a series of passive wheels to the perimeter of the newly designed joint mechanism with 3 DOFs, a snake-like robot provided with the characteristic of omnidirectional mechanism can traverse rough terrain and compensate the lack of actuation due to passive wheels. The nonholonomic constraints and kinematics are analyzed as well as the redundancy. The composite motion method and grouping alternation motion control method are thus proposed for the locomotion of robot and the avoidance of singularity. Also, the grouping alternation motion adds a new explanation to the sinus lifting locomotion of natural snake. Computer simulations validate both mobility of mechanism and effectiveness of control methods.

Development of a shape shifting robot for search and rescue

A novel link-type modular robot, which can change its shape, has been developed for potential application in urban search and rescue (USAR) operation. The advantages of the robot with link-type structure have been specified, and its shape shifting principle has been discussed. A three-module shape shifting robot has three kinds of symmetry configurations, that is, line type, triangle type and row type. Each configuration possesses its unique mobility. A tracked prototype has been built and tested under various unstructured environment Experiments have demonstrated its mobility and flexibility.

Mechanical design and dynamic analysis of planetary rover

For improvement of planetary rover locomotion, a new type of tracked vehicle was designed for planetary exploration based on the concept of reconfigurability. By applying the planetary wheel principle, the system can give output in different forms under various constraint conditions. As a reconfigurable module, the vehicle can be integrated into a larger system using two basic configurations. As a stand-alone rover, it has two moving modes. The whole design was analyzed by conducting dynamics simulations and experiments

Path planning of a snake-like robot based on serpenoid curve and genetic algorithms

The path of the snake-like robot has no repetition because its motion is influenced by manifold indeterminate factors such as ground condition, mechanisms vibration and motor voltages variety. A novel path planning technique based on serpenoid curve and genetic algorithms (GAs) has been proposed to control the snake-like robot in Shenyang Institute of Automation (SIA, China). First, the ranges of the path and the curvature deviation have been calculated approximately and set as the bounds of genetic algorithms. Then using real time dual genetic algorithms, this path planning technique not only can decide the shortest path and the minimum curvature deviation, but also can limit the motion errors influence. Simulation results show that the results of the second layer of GAs are more available than that of the first layer of GAs and this novel technique is effective for the path planning of the SIA snake-like robot.

Coupled-drive-based joint design of a snake robot and its body-lifting method

Snake robots have very strong environmental adaptability. The locomotion and inspection of the robots depend upon their ability of climbing over obstacles and the lifting height. Especially in the rescuing application, the higher the robot can lift the more information can be obtained. A novel joint mechanism thus has been designed, that has 3 degrees of freedom among which 2 degrees of freedom are driven through a coupled drive. The snake robot composed of these joints can get a larger moment and a larger workspace. In this paper, we present the principle of the joint design that is based on a coupled drive, and introduce the lifting method of the snake robot and the effect of maximal joint angle /spl alpha/. Through analysis, we know that the number of units that the snake robot can possibly lift is the square of the number of units that the snake-like robot can directly lift. This is also confirmed by a simple example.

Twist-related Locomotion of a 3D Snake-like Robot

As a hyper-redundant robot, a 3D snake-like robot can perform many other configurations and types of locomotion adapted to environment except for mimicking the natural snake locomotion. The natural snake locomotion usually limits locomotion capability of the robot because of inadequacy in the mechanism and actuation to imitate characters of natural snake such as the too many DOFs and the characteristics of the muscle. In order to apply snake-like robots to the unstructured environment, the researchers have designed many gaits for increasing the adaptability to a variety of surroundings. The twist-related locomotion is an effective gait achieved by jointly driving the pitching-DOF and yawing-DOF, with which the snake-like robot can move on rough ground and even climb up some obstacles. In this paper, the twist-related locomotion function is firstly solved, and simplified to be expressed by sine or cosine function. The 2D locomotion such as V-shape and U-shape is achieved. Also by applying it to the serpentine locomotion or other types of locomotion, the snake-like robot can complete composite locomotion that combines the serpentine locomotion or others with twist-related locomotion. Then we extend the twist related locomotion to 3D space. Finally, the experimental results are presented to validate all above analyses