Haptic Control Algorithm Research Articles

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.

Haptic control of steer-by-wire systems for tracking of target steering feedback torque

This study proposes a haptic control of steer-by-wire systems for tracking a target steering feedback torque to achieve the conventional steering feedback torque. The haptic feedback control with a steer-by-wire steering-wheel system model was used to provide drivers with a conventional steering feedback torque. The steer-by-wire steering-wheel system model was developed, and a haptic control algorithm was designed for a desired steering feedback torque with a three-dimensional target steering torque map. In order to track the target steering torque to let the drivers feel the conventional steering efforts, an adaptive sliding-mode control was used to ensure robustness against parameter uncertainty. The angular velocity and angular acceleration used in the control algorithm were estimated using an infinite impulse response filter. The performance of the proposed controller was evaluated by computer simulation and hardware-in-the-loop simulation tests under various steering conditions. The proposed haptic controller successfully tracked the steering feedback torque for steer-by-wire systems.

Stability enhancement of haptic interaction by frequency-dependent damping and its application to scaled teleoperation

This paper presents a frequency-dependent damping element, called an analog input shaper (AIS), to improve the stability of haptic interaction with virtual or real environments. High frequency inputs to a haptic interface, which usually occur in the collision with very stiff objects, can bring limit cycle oscillations and instabilities. In order to reduce these high frequency inputs and thus to improve the stability of haptic interaction, the AIS is added to the haptic system. Moreover, the AIS is applied to a passivity-based haptic stability control algorithm, called an energy-bounding algorithm (EBA), to increase the displayed impedance range by the EBA. Through scaled teleoperation experiments using an atomic force microscope (AFM), we show that the AIS can enhance stability during haptic interaction and consequently increase impedance range that a haptic interface can stably display. Also, we show that the AIS can alleviate conservativeness of the passivity-based haptic control algorithms.