Time base generator

Abstract: A novel chattering-free dynamic sliding mode controller for a class of uncertain mechanical systems is proposed in order to account globally for a time-varying sliding regime for all time and for any initial condition. The new sliding surface, parametrized by a time base generator, plays the role of moving, and rotating continuously the nominal sliding surface, while shifting is done through a known, state-independent, vanishing vector to eliminate the reaching phase for any initial condition, a weaker assumption in comparison to some moving sliding surface designs. In this way, the closed-loop system yields finite-time convergence of tracking errors, whose convergence time can be fixed independently of initial conditions, in contrast to terminal sliding mode wherein convergence time depends on initial conditions. To implement the controller, the upper bound of the derivative of the sliding surface is required, a weaker assumption in contrast to some dynamic sliding mode controllers. The performance of the closed-loop system is visualized through simulation.

Abstract: In the framework of a central hypothesis of kinematic invariance, we propose a model (ξ-model) which is a non-linear dynamical system capable of generating, as motor primitives, a family of curved trajectories. The model links shape and speed by means of a suitable time base generator that drives two equations: a linear-speed equation and a turning-speed equation.

Abstract: A time-base generator with a self-compensating control loop. The time-base generator is suitable for use in level measurement and time-of-flight ranging systems. The time-base generator includes a pulse generator stage, a delay stage, a control loop and a references voltage module. The pulse generator generates a transmit pulse train and a receive or sampling pulse train with a delayed timing relationship. The control loop functions with the delay stage to maintain the desired delay between the first pulse train and the second pulse train. According to another aspect, the time-base generator includes a calibration module. The calibration module generates calibration pulses which are used by the controller in the level measurement system to calibrate operation.

Abstract: This paper presents a new control strategy of the artificial potential field approach to a real-time motion planning problem in a known environment. In the artificial potential approach, the goal is represented by an attractive artificial potential and the obstacles are represented by a repulsive one, so that a robot reaches the goal without colliding with obstacles by using a gradient technique such as the steepest descent method. Although this approach is quite simple and computationally much less expensive than other methods based on the global information on the task space, so far few attentions have been paid to dynamic behavior of the generated trajectories such as movement time from the initial position to the goal and the velocity profile of the end-effector motion. In the present paper, we argue that the dynamic behavior of the arm trajectory to be generated should be taken into account within the framework of the artificial potential field approach, and introduce a time base generator that acts as a time varying gain and determines a dynamic behavior of the arm motion. By synchronizing a potential function used in the artificial potential field with the time base generator, convergence time of the generated arm trajectory can be adjusted through the time base generator without any change of the potential function itself.