Tele-operation of a Mobile Robot Using a Force Reflection Joystick with a Single Hall Sensor

Abstract

Though the final goal of mobile robot navigation is to be autonomous, operators' intelligent and skillful decisions are necessary when there are many scattered obstacles. There are several limitations even in the camera-based tele-operation of a mobile robot, which is very popular for the mobile robot navigation. For examples, shadowed and curved areas cannot be viewed using a narrow view-angle camera, especially in bad weather such as on snowy or rainy days. Therefore, it is necessary to have other sensory information for reliable tele-operations. In this paper, sixteen ultrasonic sensors are attached around a mobile robot in a ring pattern to measure the distances to obstacles. A collision vector is introduced in this paper as a new tool for obstacle avoidance, which is defined as a normal vector from an obstacle to the mobile robot. Based on this collision vector, a virtual reflection force is generated to avoid the obstacles and then the reflection force is transferred to an operator who is holding a joystick to control the mobile robot. Relying on the reflection force, the operator can control the mobile robot more smoothly and safely. For this bi-directional tele-operation, a master joystick system using a hall sensor was designed to resolve the existence of nonlinear sections, which are usual for a general joystick with two motors and potentiometers. Finally, the efficiency of a force reflection joystick is verified through the comparison of two vision-based tele-operation experiments, with and without force reflection.

Implementation of remotely controllable mobile robot system over mobile ad-hoc network

“…A restaurant service mobile robot equipped with camera, speaker, sensors and laser positioning system for fast and precise positioning and guidance is developed in [1] to transfer dishes to the customers. In paper [3], a bidirectional teleoperation system is presented where the slave robot receives the user's command through the joystick and sends back the environment information to the user as a feedback force. A full-duplex point-to-point communication between a PC and the mobile robot using Bluetooth technology is used to implement the real time operation in [8].…”

“…The bottom deck contains a 12V lead acid battery, two DC motors to drive each wheel via a gearbox, fuses from the battery to the embedded controller, and 500ppr encoders attached directly to each wheel shaft. Differential steering is accomplished by driving each wheel separately allowing turning on the spot, curves and forward/backward motion of the robot like [1], [3], [8] etc. The middle deck contains an embedded microcontroller, three ultrasonic transducers, led indicators, and a motor driver for the DC motors.…”

“… Introducing the haptic feedback mechanism to improve user's performance in terms of number of collisions, navigation time etc. as discussed in [3], [14].  An easy way to support the video capability on the target robot is by installing an instant messaging application e.g.…”

“…In the presence of many scattered obstacles or in critical applications where intelligent decisions are required dynamically, the autonomous mode cannot be relied on. Instead a tele-operated control system where a human user directly controls the robot according to his decision is utilised [3].…”

Force feedback assisted balancing of inverted pendulum under manual control

“…As an important interactive method, force/haptic interaction has been studied extensively in human-machine system. Haptics/force has been used to enhance perception and provide assistance to operators [2]. In [3], A. K. Ko proposed a haptic interface which was used to increase the performance of remote work.…”