Stepping Over Virtual Obstacles with an Actuated Gait Orthosis

The rehabilitation robot LOKOMAT has been developed at University Hospital Balgrist to automate treadmill training of spinal cord injury and stroke patients. Current rehabilitation training on that robot consists of moving the patient's legs on predefined trajectories. However, this kind of training is not challenging, as patients are moved regardless of their efforts and do not see their advancement. To enhance rehabilitation training with the LOKOMAT, a virtual reality setup was installed. It consists of a passive stereo projection system (screen size 3 m times 2 m), a Dolby 5.1 sound system and an electric fan. With that setup an obstacle crossing scenario was implemented. The patients can see their advancement on the screen, as an animated figurine (avatar) moves along a path simultaneously with their own movements. Additionally they can hear sounds (e.g. environmental sounds, steps), feel the wind, and experience force feedback, provided by the orthosis, when hitting obstacles. The objective of a first study on visual feedback was to investigate which feedback suits best to perceive the obstacle distances and heights correctly. To answer this question, 14 healthy subjects walked in the actuated gait orthosis, received visual feedback and tried to avoid collisions with obstacles. Subjects could move freely within the gait orthosis and determine their own speed and step length. They had to cross the obstacles independently, with haptic feedback, indicating obstacle hits. Results show that the side view results in least obstacle hits and that 2D excels 3D display in this respect