Robot-assisted activities of daily living (ADL) rehabilitation training with a sense of presence based on virtual reality

Abstract. ​​​​​​​The integration of virtual reality (VR) technology with rehabilitation robots significantly improves rehabilitation training effectiveness. Although most studies employ VR games to engage patients, few explore activities of daily living (ADL) that incorporate visual, auditory, and force feedback. This article discusses the use of Unity software and a 4-degree-of-freedom upper-limb rehabilitation robot to design a picking and placing training exercise that provides a sense of presence. An inverse kinematics algorithm creates a virtual character to simulate realistic actions and perspective changes. Encouraging prompts and sounds motivate patients, while initial load and friction compensation renders the robot transparent. Virtual objects are assigned different masses, transmitted via the User Datagram Protocol (UDP) and converted into air pressure, allowing a cylinder to generate downward force, simulating gravity. Upper-limb electromyography (EMG) signals are collected during training. The experiment results show that air pressure increases within 1 s to provide a sensation of gravity. Picking up various objects generates distinct EMG signals, with amplitude and variation comparable to dumbbell experiments. This suggests that the proposed ADL training effectively exercises the joints and muscles of the upper extremities, providing high realism in vision and force perception.