| Author | Niphon Lapanaphan |
| Note | A dissertation submitted in partial fulfillment of the requirements for the
degree of Doctor of Engineering in
Mechatronics |
| Publisher | Asian Institute of Technology |
| Abstract | In a conventional haptic system, haptic applications have mostly relied on active actuators. To deal with high impedance rendering issues, many of the previous researches in haptic were concentrated on control methodologies and modeling techniques to improve stability and performance. The aforementioned researches involved complex mathematical calculations and detailed computer programming, yet impedance rendering was not satisfactorily high. Moreover, overshoots and other conditions leading to instability were still the most concern for such haptic applications as robotic surgery, surgical training, etc. The goal of this research was to present a novel concept of high impedance actuator fusion (HIAF) to increase the impedance and stability in a haptic system by using a motor, a damping brake (DB), and a magnetic brake (MB). The approach utilized the unique characteristics of the actuators to manipulate the system variables in a more stable way. The system was modeled as a linear time-invariant system with an impedance control methodology. A new stability condition was defined, and some selected simulations and haptic experiments were presented for the case of a 1-DOF haptic device. The first experiment was intended to examine the stability improvement on the haptic system by HIAF. A benchmark of a virtual wall was defined as a bilateral constraint, and a pulse torque was applied to disturb the system stability without the presence of human operator. A conventional virtual wall stiffness gain (Ks) was increased from 0 until instability occurred. Then, a damping variable (Be) controlled via DB and a friction variable (fm) controlled via MB were added. The results showed that HIAF increased the stable stiffness of the virtual wall over 40 times, compared to a conventional haptic system using only a single motor. Another experiment was aimed to investigate the reaction between a human operator and the haptic system with HIAF. The virtual wall was differently defined as a unilateral constraint. The experimental objectives were mainly divided into two parts, the first of which was to observe the overshoot of a step response in the transient state by the added controllable damping. The results showed that increasing Be decreased the percentage of overshoot (PO) from 24% to 8% at Ks = 10 N.m/rad (309 N/m) and from 30% to 15% at Ks = 20 N.m/rad (13.3 kN/m). Further increasing of Be made PO even smaller and eventually vanish. The second part was to explore the impedance boundary in the steady state by the added controllable friction. The results showed that the impedance limit against an operator input torque (To) increased with increasing fm and increased further with larger Ks. HIAF extended To from 3 to 7 N.m at Ks = 10 N.m/rad and from 6 to 10 N.m at Ks = 20 N.m/rad. The value of fm beyond 10 N.m yielded so high impedance that the operator felt difficult to overcome. |
| Year | 2017 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Microelectronics (ME) |
| Chairperson(s) | Bohez, Erik L. J.;Mongkol Ekpanyapong; |
| Examination Committee(s) | Guha, Sumanta;Song Weon Keun;Khatib, Oussama ; |
| Scholarship Donor(s) | Royal Thai Government;AIT Fellowship; |
| Degree | Thesis (Ph.D.) -- Asian Institute of Technology, 2017 |