Robotic hand posture and compliant grasping control using operational space and integral sliding mode control

This paper establishes a novel approach of robotic hand posture and grasping control. For this purpose, the control uses the operational space approach. This permits the consideration of the shape of the object to be grasped. Thus, the control is split into a task control and a particular optimizing posture control. The task controller employs Cylindrical and Spherical coordinate systems due to their simplicity and geometric suitability. This is achieved by using an Integral Sliding Mode Controller (ISMC) as task controller. The ISMC allows us to introduce a model reference approach where a virtual mass-spring damper system can be used to design a compliant trajectory tracking controller. The optimizing posture controller together with the task controller creates a simple approach to obtain pre-grasping/object approach hand postures. The experimental results show that target trajectories can be easily followed by the task control despite the presence of friction and stiction. When the object is grasped, the compliant control will automatically adjust to a specific compliance level due to an augmented compliance parameter adjustment algorithm. Once a specific compliance model has been achieved, the fixed compliance controller can be tested for a specific object grasp scenario. The experimental results prove that the BERUL hand can automatically and successfully attain different compliance levels for a particular object via the ISMC. G. Herrmann is with the Bristol Robotics Laboratory, Faculty of Engineering, Department of Mechanical Engineering, University of Bristol, BS8 1TR, United Kingdom, [email protected]. J. Jalani is with the Department of Electrical Engineering Technology, Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia, 86400, Parit Raja, Batu Pahat, Johor, Malaysia. M.N.Mahyuddin is with the School of Electrical and Electronics Engineering, Universiti Sains Malaysia, Pulau Pinang, Malaysia. S. G. Khan is with the Department of Mechanical Engineering, College of Engineering Yanbu, Taibah University, Saudi Arabia. C. Melhuish is with the Bristol Robotics Laboratory, University of the West of England, Bristol, BS34 8QZ, United Kingdom. 1