Combining Load and Motor Encoders to Compensate Nonlinear Disturbances for High Precision Tracking Control of Gear-Driven Gimbal

Abstract

High-performance position control can be improved by the compensation of disturbances for a gear-driven control system. This paper presents a mode-free disturbance observer (DOB) based on sensor-fusion to reduce some errors related disturbances for a gear-driven gimbal. This DOB uses the rate deviation to detect disturbances for implementation of a high-gain compensator. In comparison with the angular position signal the rate deviation between load and motor can exhibits the disturbances exiting in the gear-driven gimbal quickly. Due to high bandwidth of the motor rate closed loop, the inverse model of the plant is not necessary to implement DOB. Besides, this DOB requires neither complex modeling of plant nor the use of additive sensors. Without rate sensors providing angular rate, the rate deviation is easily detected by encoders mounted on the side of motor and load, respectively. Extensive experiments are provided to demonstrate the benefits of the proposed algorithm.

Hybrid Motor System for High Precision Position Control of a Heavy Load Plant

“…Not only the mechanism needed for the lift up and press system is vital, but the controller is also an important part of the system. A number of control design techniques have been developed [1,[3][4][5][6][7][8][9][10][11]17]. Most researchers tried to verify the model's uncertainties and nonlinear friction and then developed a controller algorithm to compensate for them.…”

“…High precision performance demands have quickly increased due to the needs of improving both quality and speed [3][4]. Many types of actuators such as DC/AC motors or stepping motors with ballscrew/lead-screws, piezoelectric actuators as well as pneumatic or hydraulic actuators are used to develop high precision positioning systems [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Also, many sophisticated control techniques such as adaptive control [4][5]17], friction compensation [6], and slide mode control [7][8] have been developed to improve systems performance and to support manufacturing processes.…”

“…Also, the friction in the system would vary in a large range. The increasing demand on the performance and cost of the lift up and press system has driven researchers to develop a mechanism and control technique to improve the performance of the system [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

“…This mechanism can be used to lift up and down a heavy load such as a vehicle. However, it is not easy to precisely control the position of the system because of gear backlash, flexibility and hysteresis [11]. Also, this problem cannot be easily solved by designing an advanced control technique.…”

Experimental Investigation of Linear Encoder’s Subdivisional Errors under Different Scanning Speeds

“…Due to their high accuracy, resolution, and repeatability, as well as their ability to work under different environmental conditions and their relatively low price, they are used in a variety of applications. Some examples are manually controlled machine tools and computer-numericalcontrol (CNC) machines [1][2][3][4], robotics [5][6][7][8][9][10], servosystems [11][12][13][14], monitoring and fault diagnosis systems [15][16][17][18], tracking systems [19,20], linear and rotary positioning stages [21][22][23][24], and other precision-positioning applications [25].…”