Design for Sensorless Force Control of Flexible Robot by Using Resonance Ratio Control Based on Coefficient Diagram Method

Abstract

Original scientific paperGenerally, the flexible robot system can be modeled as the two-mass system which consists of a motor and load connected by a spring. Thus, its elasticity causes resonance in the system. By using the conventional PID controller, this method cannot perform well in this situation. Much research has proceeded with the aim of reducing vibration. A new effective control method, the resonance ratio control, has been introduced as a new way to guarantee the robustness and suppress the oscillation during task executions for a position and force control. In this paper, three techniques are proposed for improving the performance of resonance ratio control. Firstly, a new multi encoder based disturbance observer (MEDOB) is shown to estimate the disturbance force on the load side. The proposed observer is not necessary to identify the nominal spring coefficient. Secondly, coefficient diagram method (CDM) has been applied to calculate a new gain of the force controller. A new resonance ratio gain has been presented as 2.0. Finally, the MEDOB and load side disturbance observer (LDOB) are employed to identify a spring coefficient of flexible robot system. By using the proposed identification method, it is simple to identify the spring coefficient and easy to implement in the real flexible robot system. The effectiveness of the proposed identification method is verified by simulation and experimental results.Key words: Disturbance observer, Two-mass system, Coefficient diagram method, Resonance ratio control Sinteza bezsenzornog upravljanja silom za fleksibilnog robota korištenjem upravljanja omjerom rezonancija temeljenim na metodi koeficijentnog dijagrama. Općenito, sustav fleksibilnog robota može se modelirati kao dvomaseni sustav koji se sastoji od motora i tereta povezanih oprugom. Rezonancija sustava posljedica je elastičnosti opruge. Korištenje konvencionalnog PID regulatora ne daje zadovoljavajuće performanse u ovoj situaciji. Provedena su mnoga istraživanja s ciljem smanjenja vibracija. Tako je uvedena nova učinkovita metoda upravljanja, upravljanje omjerom rezonancija, kao novi način da se osigura robusnost i priguše oscilacije tijekom izvršavanja zadatka putem upravljanja pozicijom i silom. U ovom radu predložene su tri tehnike za poboljšanje performansi upravljanja omjerom rezonancija. Prvo, pokazano je kako novi observer poremećaja temeljen na više enkodera (MEDOB) estimira poremećajnu silu na strani tereta. Predloženi observer nije nužan za identifikaciju nominalnog koeficijenta opruge. Drugo, metoda koeficijentnog dijagrama (CDM) je primijenjena za proračun novog pojačanja regulatora sile. Iznos 2.0 je odre en kao novo pojačanje omjera rezonancija. Konačno, MEDOB i observer poremećaja na strani tereta (LDOB) korišteni su za identifikaciju koeficijenta opruge sustava fleksibilnog robota. Predložena metoda identifikacije jednostavna je za implementaciju na stvarni sustav, te se pomoću nje jednostavno identificira koeficijent opruge. Učinkovitost predložene metode identifikacije provjerena je...

Backdrivability Improvement Method Based on Angular Transmission Error in a High Reduction Gear

“…Therefore, the consideration of the torsion torque as the connecting element for the motor and load sides is needed when the reduction gear is driven. However, in the proposed method of this paper, the feedforward friction compensation (11) and the MEDOB (12) are applied which do not use the torsion stiffness. In addition, we propose the assist control based on the backlash that is not related to the torsional torque.…”

“…τ f s and τ f c are the maximum static friction and the Coulomb friction respectively,θ s and Δθ are the Stribeck angular velocity and the micro angular velocity respectively; and D v is the viscous friction coefficient. (12) In describing the MEDOB, the motor torque becomes τ M = τ M + τ f model by separating the feedforward friction compensation and others. When the effect of friction is compensated by the feedforward friction compensation, Eq.…”

“…To this end, it reduces the friction in the reduction gear by feedforward friction compensation (11) . It also feedbacks the load-side external torque, which is estimated by a multi-encoder-based disturbance observer (MEDOB) (12) . A backdrive assist control that moves the motor based on the a) Correspondence to: Kenta Nagano.…”

Torque-Sensorless Control for a Powered Exoskeleton Using Highly Back-Drivable Actuators

“…We used a multi-encoder-based disturbance observer (MEDOB) [11] as the external torque estimation method in the double inertia system. Using MEDOB, the torqueτ d is estimated by the following equation:…”

A Coefficient Diagram Method Controller with Backstepping Methodology for Robotic Manipulators

“…Different CDM controllers have been proposed for linear system [4][5][6]. But, CDM controllers' essential shortage is her limitation to linear system and the needing of exponential stability for a given nonlinear systems.…”