A New Approach to Haptic Rendering by Position Control

Abstract

Conventional force rendering methods in haptic applications often suffer stability issues when simulating stiff objects such as a virtual wall. This paper argues that the emphasis in such scenarios is to minimize the penetration into the virtual wall instead of emulating the force to the operator. Therefore, position controllers are developed to achieve better haptic rendering of the virtual wall. The new rendering method is implemented on a complex 6-DOF parallel structure haptic device. The position controllers are developed by both LQR and 6-joint independent PID methods. The control method exploits model-based development tools to obtain the linear control system model without deriving the mathematical model of the complex haptic device. The performance of the two controllers is compared on a simulated prototype of the haptic device.

A Position-Control Based Approach to Haptic Rendering of Stiff Objects

“…In this paper, we continue to develop the approach presented in a previous paper [27]. We have selected a simple but representative case where we render the interaction with an ideal stiff wall with infinite stiffness as an initial step for investigating the formulated research questions.…”

“…The angle of joint 6 is denoted q6 in Figure 1, providing an up-down motion for Chain 3. In the previous paper [27], the researchers found that joint 6 can have a different behavior due to the possibility that most of the gravity of TAU is compensated by it, making it work closer to the saturation limit. To illustrate this possibility, Figure 11 shows the joint torque on joint 6 for two different QPs.…”

A Joint-space Position Control-based Approach to Haptic Rendering of Stiff Objects using Gain Scheduling

“…In this section, we first introduce the test case device for the paper and then, the proposed approach is recapped as it originates from previous work [33,34].…”

“…For step 4 of force computing, stiff objects are mostly modeled as a spring-damper system and this can lead to unstable behavior if not dealt with carefully. To avoid the shortcomings of using a spring-damper system, we propose a positioncontrol based approach as a solution to achieve a stable interaction with stiff objects [33]. A new user scenario is introduced in this paper.…”