Upper limb motion profile during small to medium time-limited reaching tasks in A VR based robotic training environment

In the area of rehabilitation robotics, many researchers have investigated the therapeutic effects of forces that are proportional to the difference of the user's hand trajectory with an optimum trajectory that is usually based on the Minimum Jerk Model (MJM). Forces applied in different studies were based on MJM trajectory variables, e.g., velocity, acceleration, position, etc. Consequently, MJM is a key component for upper limb robotic rehabilitation. However, it is critical to establish the validity of this model in the working environment prior of employing it as a reference control function. This work investigates the validity of the MJM under a haptic-virtual environment. The original 'real' tests (with no obstacles) that were employed for validating the MJM in planar motion are duplicated in a virtual environment. Haptic feedback is achieved with the use of a Phantom 1.5 High Force haptic interface. Experiments with healthy users are performed to investigate the validity of the MJM in virtual reality conditions. The experiments demonstrated that the MJM is also valid in virtual environments. Nevertheless it was found that in the virtual world, higher time durations are required for completing the tasks than in the real world. The results of this work will be used in the design of haptic-virtual environments for the rehabilitation of upper limbs of people with neuro-disabilities. Therapeutic forces based on the MJM can be applied given that the Minimum Jerk Model is valid in virtual environments.