Force control for position interface industrial manipulator working in unknown environment

Industrial manipulators have multidisciplinary applications. The use of industrial manipulators has increased rapidly, and they are more refined in many applications due to advances such as fast response time, high precision, high speed motions and a high level of performance. Most industrial manipulators are position controlled; usually vision and force sensors are not integrated in most commercial industrial robots. Therefore in order to use industrial manipulators for delicate tasks, the addition of force and vision sensing mechanisms is required to successfully automate these tasks, and to enable robots to avoid high contact forces while working in applications that require contact with environments. In this paper, an optical tracking device and a force torque sensor were integrated into a position controlled industrial manipulator to operate in unknown inclined planes. In addition, two types of controllers are presented to control the interaction force. The control techniques are admittance control and fuzzy logic control. The results show the capability of the presented controllers to successfully monitor the interaction force while tracking the position of a passive marker moved by a human operator. The force error using the admittance controller is found to be in the range of ±0.75 N. The fuzzy logic controller on the other hand produces less overshoot relative to the admittance controller, but a higher error of ±1.5 N.