Force Control for One Degree of Freedom Haptic Device using PID Controller

Haptics has been used as an additional feedback to increase human experience to the environment over years and its application has been widening into education, manufacturing and medical. The most developed haptic devices are for rehabilitation purposes. The rehabilitation process usually depends on the physiotherapist. But it requires repetitive movements for long-term rehabilitation, thus haptic devices are needed. Most of the rehabilitation devices are include haptic feedback to enhance therapeutic outcome during the rehabilitation process. However, the devices typically incorporate multiple degrees of freedom (DOF), complex design, and are costly. Rehabilitation for hand movement such as grasping, squeezing, holding and pinching usually does not need an expensive and complex device. Therefore, the goal of this study is to develop a simple one DOF Haptic Device for grasping rehabilitation exercise. The performance of the haptic device is tested with different conventional controllers, such as Proportional (P) controller. Proportional-Integral (PI) controller, Proportional-Derivative (PD) controller and Proportional-Integral-Derivative (PID) controller, to obtain the best proposed controller based on the lowest value of Mean Square Error (MSE). The results show that PID Controller (MSE = 0.0028) is the most suitable for the haptic device with Proportional gain (K-p), Integral gain (K-i) and Derivative gain (K-d) are 1.3, 0.01 and 0.2 respectively. The force control algorithm can imitate the training motion of grasping movement for the patient.