A position control-based approach to haptic rendering of stiff objects using piece-wise linear model

In traditional force rendering approaches, it is quite popular to model a virtual stiff wall as a spring-damper system to compute the interaction force, which can easily lead to unstable behavior. In this paper, we present an approach to ensure no penetration into the wall by position control. The approach approximates the nonlinear model of a 6-DOF parallel-structure haptic device by a piece-wise linear model to improve the performance compared with a controller designed from a one-point linearized model in haptic rendering. A simulation-based performance comparison study shows that the new controller can render higher stiffness than the previous solution.

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

Haptic rendering often deals with interactions between stiff objects. A traditional way of force computing models the interaction using a spring-damper system, which suffers from stability issues when the desired stiffness is high. Instead of computing a force, this paper continues to explore shifting the focus to rendering an interaction with no penetration, which can be accomplished by using a position controller in the joint space using the encoders as feedback directly. In order to make this approach easily adaptable to any device, an alternative way to model the dynamics of the device is also presented, which is to linearize a detailed simulation model. As a family of linearized models is used to approximate the full dynamic model of the system, it is important to have a smooth transition between multiple sets of controller gains generated based on these models. Gain scheduling is introduced to improve the performance in certain areas and a comparison among three controllers is conducted in a simulation setup.

Haptic force rendering of rigid-body interactions: A systematic review

Haptic rendering has been developing for decades with different rendering approaches and many factors that affect the stability when rendering rigid-body interactions have been investigated. To get an overall understanding of the challenges in haptic rendering, we approach this topic by conducting a systematic review. This review examines different haptic rendering approaches and how to deal with instability factors in rendering. A total of 25 papers are reviewed to answer the following questions: (1) what are the most common haptic rendering approaches for rigid-body interaction? and (2) what are the most important factors for instability of haptic rendering and how to address them? Through the process of investigating these questions, we get the insight that transparency can be further explored and technical terms to describe haptic rendering can be more standardized to push the topic forward.

Haptic control of steer-by-wire systems using parameter estimation of rack system lateral load model

This paper describes a haptic control of steer-by-wire systems for rendering the conventional steering system under various road conditions using parameter estimation of rack system lateral load model. To design the conventional steering system model, the dynamic model of a rack system has been developed as a mass-spring-damper system with a friction model. An online parameter estimation of the rack system was designed to consider the various road conditions in the haptic rendering. In a steering wheel system, which is a haptic device, a limit cycle, and instable behavior can occur due to the sampling rate and quantization. To prevent the limit cycle and instable behavior, a passivity analysis was conducted and constraint conditions of the rendering coefficient was derived. The haptic control algorithm is designed to render the conventional steering system without limit cycles using passivity conditions. The performance of the proposed controller was evaluated via both computer simulations and vehicle tests under various steering conditions. The results demonstrate that the proposed algorithm ensures haptic rendering performance on dry and wet asphalt conditions.