SUMMARYThis paper presentsan adaptive actuator failure compensation method, which compensates for uncertainties due to unknown actuator failures for redundant manipulator systems. The method is first developed for manipulators whose joints are concurrently actuated. While physical realization of concurrently actuated manipulators and the advantages of their use have been understood before, in this paper failure modeling, controller structure, and adaptive update rules for handling uncertainties from the actuator failures are studied. The adaptive actuator failure compensation method is then expanded for a cooperating multiple manipulator system with uncertain actuator failures. Dynamic equations of such a multiple manipulator system in the task space are derived and the adaptive actuator failure compensation problem is formulated in the task space, for which a compensation controller structure is proposed with stable adaptive parameter update laws. The adaptive control scheme is able to compensate for the uncertainties of system parameters and actuator failures in a more general sense. For both cases, closed-loop system stability and asymptotic tracking are proved, despite uncertain system failures.
SUMMARYThis study concerns the design and prototype of four different mobile robot platforms for rescue robot operations after an earthquake. At first, a test field is constructed to represent a mildly damaged earthquake zone. The test field consists of eight different sections: sand, gravel, ditch, water, bridge, incline, decline, and turn. The mechanical structure, electronics, software, communication, and possible sensory systems are explained. After the robots are manufactured, they are physically tested for their performance in the test field for 18 different parameters. The test results show the effective body structure. Challenges of the rescue robot design are explained and future expectations are given.
In this paper, adaptive vehicle skid control, for stability and tracking of a vehicle during slippage of its wheels without braking, is addressed. Two adaptive control algorithms are developed: one for the case when no road condition information is available, and one for the case when certain information is known only about the instant type of road surface on which the vehicle is moving. The vehicle control system with an adaptive control law keeps the speed of the vehicle as desired by applying more power to the drive wheels where the additional driving force at the non-skidding wheel will compensate for the loss of the driving force at the skidding wheel, and also arranges the direction of the vehicle motion by changing the steering angle of the two front steering wheels. Stability analysis proves that the vehicle position and velocity errors are both bounded. With additional road surface information available, the adaptive control system guarantees that the vehicle position error and velocity error converge to zero asymptotically even if the road surface parameters are unknown.
SUMMARYThis paper is an investigation of completely mechanical quick changeable joints for multipurpose explosive ordnance disposal (EOD) robots. With the assistance of a quick changeable joint, an ordinary EOD robot becomes a multipurpose robot with an end effector which can be switched during the task. This exchangeable end effector permits the robot to perform more complex duties. Making the joint completely mechanical increases its capacity and decreases its complexity of control and risk of failure. In this paper, the design, manufacturing, and testing stages are explained for four quick changeable joints each possessing different physical working principles. The test results reveal the best design for a multipurpose EOD robot and give ideas for other uses of quick changeable joints. Employing the quick changeable joints in other mobile robot applications can increase a robot's capacity and efficiency.
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