Robust force control of a hybrid actuator using quantitative feedback theory

Abstract

The use of hydraulic systems in industrial applicationshas become widespread due to their advantages in efficiency. In recent years, hybrid actuation systems, which combine electric and hydraulic technology into a compact unit, have been adapted to a wide variety of force, speed and torque requirements. A hybrid actuation system resolves energy consumption and noise problems characteristic of conventional hydraulic systems. A new, low-cost hybrid actuator using a DC motor is considered to be a novel linear actuator with various applications such as robotics, automation, plastic injection-molding, and metal forming technology. However, this efficiency gain is often accompanied by a degradation of system stability and control problems. In this paper, to satisfy robust performance requirements, tracking performance specifications, and disturbance attenuation requirements, the design of a robust force controller for a new hybrid actuator using Quantitative Feedback Theory (QFT) is presented. A family of plant models is obtained from measuring frequency responses of the system in the presence of significant uncertainty. Experimental results show that the hybrid actuator can achieve highly robust force tracking even when environmental stiffness set-point force varies. In addition, it is understood that the new system reduces energy use, even though its response is similar to that of a valve-controlledsystem.

Boundary control of container cranes from the perspective of controlling an axially moving string system

“…in the lowering process. This can be explained as follows: As seen in (32), if l is positive (i.e., the rope length is elongated), the second term enhances the stabilizing effect. But, if l is negative (i.e., the rope length is shortened), the second term will oppositely affect, that is, destabilizes the system.…”

“…Remark 4: By comparing (31) and (32), it is evident that the time rate of change of the rope energy evaluated using the definition of differentiation, (31), and the material derivative of the mechanical energy, (32), yield the same result and, henceforth, either approach can be used when evaluating the time-rate of the energy of an axially moving material. Now, based upon (25) and using the fact that, for suppressing the transverse vibration, the rigid-body-like longitudinal motion of the rope can be omitted from the stability analysis point of view of the closed-loop system, a Lyapunov function candidate is considered as follows: positive (controller) gains and d w is the target position of the gantry, which is normally given as a fixed value (i.e., 0).…”

“…The material derivatives are meaningful because of the axial transport phenomenon of the rope while hoisting the load [7,32]. Note that in (3) and (4), the dot-notation is used if the variable is a function of time only, for example, ( ), l t ( ), g y t and others.…”

A torque estimator using online tuning grey fuzzy PID for applications to torque-sensorless control of DC motors

“…The first is close-loop robust stability which must be checked with reasonable margins. The second control objective is closeloop disturbance attenuation [33]. From (12), transfer function of the PID controller as well as the system open-loop transfer function and the sensitivity function are expressed as:…”

Robust control application for a three-axis road simulator

“…Many applications, such as automotive dynamics, robotics, aerospace and MEMS area, have been made. In particular, Ahn (2007) utilized the QFT in controlling a hydraulic actuator [15] and Ha (2000) used the QFT in controlling robotics area [16].…”