Design and Control of a 3 Degree-of-Freedom Parallel Passive Haptic Device

Teleoperated robotic surgery and surgical simulation provide surgeons with tools that can improve the health outcomes of their patients. The limiting factor in many of these systems, however, is the lack of a haptic system that can render high impedance without compromising transparency or stability. To address this issue, we constructed a 3-Degree-of-Freedom haptic device using brakes as actuators. A novel controller is also proposed to increase the range of forces the device can generate and eliminate stiction. The device uses a modified Delta kinematic structure making it light and rigid. Since brakes are intrinsically stable, the device safely generates a wide range of impedance making it well suited for many surgical applications. The novel controller attempts to minimize the sum of forces acting perpendicular to the virtual surface eliminating un-smooth force output and stiction characteristic to passive devices, while increasing the range of displayable forces. The controller was validated using six testing scenarios where it rendered contact with frictionless surfaces. When using the controller, the device rendered the desired surface without stiction. Since the controller successfully rendered complex geometry, it can also work in other applications, such as robotic surgery and surgical simulation.