Development of delta robot driven by pneumatic artificial muscles

Recently, research of a haptic device that renders human arbitrary-force sense has been accelerating for application in rehabilitation and virtual reality/augmented reality devices. Generally, these devices are actuated by electric motors; however, the actuators have low stiffness output and low backdrivability. In an effort to counteract these drawbacks, we developed a delta robot actuated by straight-fiber-type pneumatic artificial muscles. This robot renders human arbitrary-force sense without force sensor feedback. Furthermore, this robot has backdrivability derived from the softness of the pneumatic artificial muscles and no backlash because the structure does not use gears. Thus, by adopting a delta mechanism as a haptic device, high stiffness output and low inertia force are realized. In this study, we introduce the development of the delta robot as the prototype of a haptic device and conduct position-control and stiffness-control experiments to examine the device´s fundamental properties. From the experimental results, we confirm that end position is controllable by both sides of static and dynamic state, and the stiffness of the end plate is controllable without feedback of the force sensor.