Showing papers by "Vicente Feliu-Batlle published in 2020"

Multi-link endoscopic manipulator robot actuated by shape memory alloys spring actuators controlled by a sliding mode

Abstract: The aim of this study was to design and evaluate a prototype of a snake-like endoscopic manipulator robot (SLEMR) and its corresponding automatic controller based on the first order sliding mode theory. The SLEMR was controlled with a set of actuators made of shape memory alloys (SMA). The SLEMR device was constructed with a sequential arrangement of links interconnected by a two degree-of-freedom joint. A parallel agonist–antagonist configuration of actuators was implemented to move each joint. The physical relation between temperature and elongation in SMA forced the execution of the movement in the joint. Elongation–temperature model of the SMA actuator served to get a feasible bound of velocity for each joint. Each pair of SMA actuators was controlled by a first order sliding mode controller. This control design solved the tracking trajectory problem for each joint in the SLEMR because of its robustness against uncertainties and external perturbations. The control action was projected into a feasible implementable set of pulse-width modulated signals which was used to regulate the temperature of the corresponding SMA actuator. The controller designed in this study was experimentally validated in a SLEMR made up by a tridimensional printing technique. The control strategy induced the successful trajectory tracking for all the joints in the SLEMR simultaneously. This characteristic of the control design also enforces the tracking of a reference position by the tip of the final link of the SLEMR. An image acquisition system was used to determine the position of the final actuator in the SLEMR. The effectiveness of the controller proposed in this study was confirmed by the evaluation of the tracking error of the final actuator which approached to a bounded region (less than 1.0 mm) near the origin in a finite-time (0.5 s).

Adaptive Sliding Mode Impedance Control of Single-Link Flexible Manipulators interacting with the Environment at an Unknown Intermediate Point

Abstract: This paper proposes an adaptive robust impedance control for a single-link flexible arm when it encounters an environment at an unknown intermediate point. First, the intermediate collision point is estimated using a collision detection algorithm. The controller, then, switches from free to constrained motion mode. In the unconstrained motion mode, the exerted force to environment is nearly zero. Thus, the reference trajectory is a prescribed desired trajectory in position control. In the constrained motion mode, the reference trajectory is determined by the desired target dynamic impedance. The simulation results demonstrate the efficiency of proposed control scheme.

Improving the contact instant detection of sensing antennae using a Super-Twisting algorithm

Abstract: Sensing antenna devices, that mimic insect antennae or mammal whiskers, is an active field of research that still needs new developments in order to become efficient and reliable components of robotic systems. This work reports a new result in the area of signal processing of these devices that allows to detect the instant of the impact of a flexible antenna with an object faster than other reported methods. Previous methods require the use of filters that introduce delays in the impact detection. A method based on the Super-Twisting algorithm is proposed here that avoids the use of these filters and reduces such delays improving the impact instant estimation. Experiments show that these delays can be reduced in more than 50%, allowing reliable estimation of the impact instant with an error of less than 5 ms in many cases requiring a limited computational effort.