Stability and transparency improvement in haptic device employing both MR-brake and active actuator

2012-12-14
Baser, Ozgur
Konukseven, Erhan İlhan
Gurocak, Hakan
An ideal haptic device should transmit a wide range of stable virtual model impedances (Z-width) with high transparency. Magneto-rheological fluid (MR) brakes are advantageous in haptic devices since they are passive actuators. However, they cannot provide high transparency and smooth interaction due to high viscous friction, residual torque, slow response, sticking and hysteresis effects. On the other hand, active actuators cannot simulate high virtual impedances stably, but provide high transparency with a closed loop control algorithm. In the proposed hybrid actuation a task divider control (TDC) algorithm was developed for torque sharing between two actuators to provide a large Z-width and improve both transparency and smoothness. The algorithm employs two parameters which were estimated experimentally and extended to entire achievable impedance range by artificial neural network (ANN) and curve fitting techniques. A 1-DOF device having an excitation motor at the user side and brushless DC motor and MR-brake in the haptic side was used in the experiments. The excitation motor is used to generate a white noise torque input to simulate a user for frequency domain transparency tests. Results of the proposed and conventional closed loop impedance control (CLIC) algorithms were compared. The proposed algorithm improves the transparency of MR-brake by eliminating its drawbacks and presents a larger Z-width than the active actuator alone.

Suggestions

Hybrid control algorithm to improve both stable impedance range and transparency in haptic devices
Baser, Ozgur; Gurocak, Hakan; Konukseven, Erhan İlhan (2013-02-01)
An ideal haptic device should transmit a wide range of stable impedances with maximum transparency. When using active actuators, transparency improvement algorithms tend to decrease the range of attainable impedances. Passive actuators can transmit high impedances stably, but are not sufficient alone for transparency. In this study, a hybrid force control algorithm employing active and passive actuators was developed to improve the stable impedance range and transparency in haptic devices. A new transparenc...
Transparency improvement in haptic devices with a torque compensator using motor current
Baser, Ozgur; Konukseven, Erhan İlhan; Gurocak, Hakan (2012-12-01)
Transparency of a haptic interface can be improved by minimizing the effects of inertia and friction through the use of model based compensators. However, the performance with these algorithms is limited due to the estimation errors in the system model and in the velocity and acceleration from quantized encoder data. This paper contributes a new torque compensator based on motor current to improve transparency. The proposed method was tested experimentally in time and frequency domains by means of an excita...
Utilization of motor current based torque feedback to improve the transparency of haptic interfaces
Baser, Ozgur; Konukseven, Erhan İlhan (2012-06-01)
In this paper motor current based torque feedback compensator is utilized in actuator space together with a closed loop impedance control algorithm instead of model based compensator to improve the transparency performance of haptic interfaces; moreover, a novel transparency evaluation metric is developed to evaluate the transparency performance of these devices. The proposed control algorithm is experimentally tested on a 1 DOF haptic device by employing a low-cost current sensor. It is also tested on a MA...
Transparency and stability performance improvement in haptic devices
Başer, Özgür; Konukseven, Erhan İlhan; Department of Mechanical Engineering (2012)
Haptic devices are evaluated in terms of transparency, stability, pose and force control accuracy. Precise velocity and acceleration estimations are needed in haptic devices for accurate simulations. This thesis firstly focuses on velocity and acceleration estimations from incremental encoders and proposes two new estimation techniques. The second goal in the thesis is transparency improvement. The transparency is a metric that shows how well a virtual model is reflected to the user. Conventional force cont...
Optimal posture control algorithm to improve the stability of redundant haptic devices
Baser, Ozgur; Konukseven, Erhan İlhan (SAGE Publications, 2013-5-9)
Stability is indispensable to haptic interfaces for the simulation of a large variety of virtual environments. On a multi-degree of freedom (multi-DOF) haptic device, the passivity condition must be satisfied in both end-effector and joint space to achieve stable interaction. In this study, a conservative passivity condition is utilized for the stability such that guaranteeing the passivity at all joints is a sufficient condition for the passivity and then stability of the whole haptic system. An optimal po...
Citation Formats
O. Baser, E. İ. Konukseven, and H. Gurocak, “Stability and transparency improvement in haptic device employing both MR-brake and active actuator,” 2012, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/38491.