Transparency and stability performance improvement in haptic devices

Başer, Özgür
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 control algorithms are not sufficient for high transparency. Therefore, as alternative, a motor current based torque feedback compensator is developed. The transparency improvement efforts by using only active actuator adversely affect stability in haptic devices. In order to improve both stability and transparency, a new hybrid control algorithm is developed by employing active actuator and passive brake. Pose and force control accuracy are mostly problematic in multi-DOF haptic manipulators. Since the deviation of any kinematic parameter in Jacobian matrix adversely affects the accuracy of pose and force control, kinematic calibration is indispensible for haptic manipulators. Besides, most of the haptic manipulators use capstan drive mechanisms in the joints due to their advantages; but cause transmission errors. Therefore, a theory is developed for the capstan drive transmission errors. Then, a closed-chain kinematic calibration technique including transmission errors is introduced for a 7 DOF haptic device. Adjustable posture ability of redundant haptic manipulators can be used for performance improvements. Finally, an optimal posture control algorithm is developed to improve the stability of the 7-DOF haptic device.


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...
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 ...
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Gurkan, E; Banks, SP; Erkmen, Aydan Müşerref; Erkmen, İsmet (2002-09-18)
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Citation Formats
Ö. Başer, “Transparency and stability performance improvement in haptic devices,” Ph.D. - Doctoral Program, Middle East Technical University, 2012.