Robust position control of ultrasonic motor using VSS observer

Intrinsic properties of ultrasonic motor (high torque for low speed, high static torque, compact in size, etc.) offer great advantages for industrial applications. However, when load torque is applied, dead-zone occurs in control input. Therefore, sliding mode controller, which is a nonlinear controller, is adopted for ultrasonic motor. The state quantities, such as acceleration, speed, and position are needed to apply the sliding mode controller for position control. However, rotary encoder causes quantization errors in the speed information. This paper presents a robust position control method for ultrasonic motor by using Variable Structure System(VSS) observer. The state variables for sliding mode controller are estimated by the VSS observer. Besides, a small, low cost, and good response sliding mode controller is designed in this paper by using a micro computer that is essential in embedded system for the developments of industrial equipments. The effectiveness of the proposed method is verified by experimental results

Robust position control of ultrasonic motor considering dead-zone

Intrinsic properties of ultrasonic motor (high torque for low speed, high static torque, compact in size, etc.) offer great advantages for industrial applications. However, when load torque is applied, dead-zone occurs in the control input. Therefore, a nonlinear controller, which considers dead-zone, is adopted for ultrasonic motor. The state quantities, such as acceleration, speed, and position are needed to apply the nonlinear controller for position control. However, rotary encoder causes quantization errors in the speed information. This paper presents a robust position control method for ultrasonic motor considering dead-zone. The state variables for nonlinear controller are estimated by a Variable Structure System (VSS) observer. Besides, a small, low cost, and good response nonlinear controller is designed by using a micro computer that is essential in embedded system for the developments of industrial equipments. Effectiveness of the proposed method is verified by the experimental results

Strategija upravljanja pozicijom ultrazvučnog motora s putujućim valom

Since a conventional controller is continuous one, control period is normally set for a long time. When applying that controller for a travelling-wave ultrasonic motor whose parameters and performance are time-varying as a result of increasing temperature and operating condition, it is consequently resulted in degradation of the control performance. In this paper, a digital control algorithm is proposed for position control of the motors to shorten the long control period to maintain the stability of the motor performance. The proposed controller is digitally implemented by a SH7125 microcomputer utilizing a high-performance embedded workshop. The state quantities such as acceleration, speed and position, which are necessary for digital implementation, are provided by a rotary encoder. However, the optical encoder causes quantization errors in the speed information. To overcome the problem, a digital Variable Structure System (VSS) observer is also included to estimate the state quantities. The control input will be calculated after comparing the measured values and the estimated values given by the VSS observer. In short, a small, low cost and fast responsive digital controller is designed, based on a digital VSS observer, by using the SH7125 microcomputer. Effectiveness and reliability of the proposed digital controller are experimentally verified.Strategija upravljanja pozicijom ultrazvučnog motora s putujućim valom Sažetak: S obzirom da je standardni regulator najčešće kontinuirani, period upravljanja obično je postavljen na duži period. Koristeći takav regulator pri upravljanju ultrazvučnim motorom s putujućim valom, čiji su parametri i svojstva vremenski promjenjivi zbog povećanja temperature i promjena uvjeta rada, rezultat su smanjena upravljačka svojstva. U ovome radu predložen je digitalni upravljački algoritam za upravljanje pozicijom motora u svrhu smanjenja dugačkog perioda upravljanja za održavanje stabilnosti svojstava motora. Regulator je implementiran koristeći SH7125 mikroračunalo uz HEW (engl. high-performance embedded workshop) okruženje. Iznosi veličina kao što su akceleracija, brzina i pozicija, nužnih za digitalnu implementaciju, dobiveni su iz rotirajućeg enkodera. Međutim, optički enkoder dovodi do greške kvantizacije kod proračuna brzine. U svrhu smanjenja tog problema, u proces proračuna iznosa varijabli uključen je VSS (engl. Variable Structure System) estimator. Upravljački ulaz računa se nakon usporedbe mjerenih i estimiranih vrijednosti dobivenih korištenjem VSS-a. Dizajniran je digitalni regulator malih dimenzija, jeftine cijene i brzog odziva, temeljen na digitalnom VSS estimatoru koristeći SH7125 mikroračunalo. Eksperimentalno je provjerena efikasnost i pouzdanost digitalnog regulatora