Hybrid control algorithm to improve both stable impedance range and transparency in haptic devices

Baser, Ozgur
Gurocak, Hakan
Konukseven, Erhan İlhan
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 transparency-Z-width plot is proposed as a way to evaluate the stable impedance range and transparency together. The hybrid control algorithm uses parameters to share the torque demand between two actuators with smooth transition. These parameters were determined and an artificial neural network (ANN) was used to extend them to the entire achievable impedance range. The algorithm was tested experimentally on a 1-DOF haptic device. The transparency experiments employed an excitation motor located at the user side of the device to evaluate various algorithms in time and frequency domains. Results showed that the proposed hybrid control algorithm enables simulation of higher range of impedances with higher transparency than the conventional algorithms.


Stability and transparency improvement in haptic device employing both MR-brake and active actuator
Baser, Ozgur; Konukseven, Erhan İlhan; Gurocak, Hakan (2012-12-14)
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 ...
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...
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...
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...
Citation Formats
O. Baser, H. Gurocak, and E. İ. Konukseven, “Hybrid control algorithm to improve both stable impedance range and transparency in haptic devices,” MECHATRONICS, pp. 121–134, 2013, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/39658.