Portable Haptic Feedback for Training and Rehabilitation

Due to the cost, size and complexity of grounded haptic devices, their use is typically limited to research environments, and industry has been reluctant to adopt them for commercial use. In contrast to grounded devices, portable haptic devices do not have such limitations. However, one of the main drawbacks is that portable devices often cannot provide the same level of realistic interaction as grounded devices. Though the feedback quality may be diminished, the work in this thesis is based on the idea that portable systems can nonetheless provide users with beneficial feedback that improves their performance in tasks related to training and motor learning. The work presented in this thesis specifically focuses on determining the effectiveness of providing portable haptic feedback for virtual reality procedural training tasks for emergency personnel and neurological rehabilitation tasks where normal haptic feedback channels are distorted or absent. In the procedural task experiment, subjects participated in simulated exercises for clearing a damaged building, using a modified commercial video game engine and USB-compatible force and vibration feedback devices. It was found that with the addition of portable haptic feedback, subjects made fewer errors and completed tasks more rapidly. These promising results were the inspiration for the next set of studies which explored the potential uses of portable haptic feedback for neurological rehabilitation. The first set of studies were performed with stroke patients who often need assistance in recovering the usage of an impaired hand. A novel hand-opening device was developed to help stroke patients open their impaired hands and pilot experiments to test, the patients' ability to control the grasp force of their impaired hand with and without haptic feedback were conducted. A wearable haptic device provided vibrotactile haptic feedback to the users' healthy hand, correlating to the grasp forces of their impaired hand. Two different approaches to provide vibrotactile feedback were used: amplitude based feedback (ABF) and event-cue based feedback (ECF). Results showed that both approaches improved subjects' performance. Subsequently, a more extensive set of experiments were conducted utilizing a portable haptic device for neurological rehabilitation with multiple sclerosis patients. First, a portable, low-cost system was developed to help multiple sclerosis patients with asymmetric impairment exert better grasp force control in manipulation tasks. The approach consisted of measuring force vectors at the fingertips of the impaired hand, computing the force imbalance among the fingers, and providing corresponding haptic signals in the form of vibration to the fingers of the opposite hand. Tests conducted on 24 multiple sclerosis patients indicated that for those with mild impairment, slightly better results were obtained with an "event cue" feedback that alerted them when the grasp forces were straying outside of a desirable range. For patients with severe impairment, better results were obtained by providing a proportional signal, in which the frequency and duty cycle of vibration pulses were correlated directly with the magnitudes of the fingertip forces. Post-test surveys of the patients supported this observation, showing that mildly impaired subjects preferred event-cue feedback and more severely impaired subjects preferred the proportional feedback.