Abstract
Position control is usually achieved using a position controller and a profile generator. The profile generator produces a desired position trajectory from a position reference and predefined profiles. The position controller forces the actual position to trace the generated position trajectory. A time-based profile generator is the most famous profile generator due to its capability of generating various profiles. However, time base difference in analysis and implementation causes a steady-state error. In order to remove the steady-state error, this paper proposes a novel profile generator for a trapezoidal velocity profile generation. The proposed generator is based on a cascaded P-PI position controller which is designed to trace the position reference. A dynamic range limiter is adopted to provide the acceleration and velocity restrictions which are basic functions for generating the trapezoidal profile. In spite of these restrictions, it cannot make a desired velocity profile only using the limiter because deceleration point is inaccurate. To adjust the deceleration point, a feedback compensator is designed which requires the velocity of the deceleration point. The velocity of the deceleration point is estimated from the initial position error. The compensator moves the deceleration point to the appropriate point which can generate the desired velocity profile. The proposed profile generator can remove the steady-state error, and the position response can be easily adjusted to be either overdamped or underdamped by selecting the two gains appropriately. Several experimental results are presented to verify the usefulness of the proposed generator.
Highlights
Position control is a widely used control strategy in many applications such as elevators, machine tools, and robots
The residual vibrations of the S-curve profile can be reduced by an asymmetrical S-curve (AS-curve) and a high order polynomial S-curve profiles
To remove the reference error of the time-based profile generator for producing the trapezoidal profile, this paper proposes a novel profile generator based on a cascaded P-PI position controller
Summary
Position control is a widely used control strategy in many applications such as elevators, machine tools, and robots. Acceleration, velocity and position profiles are produced This method is suitable for generating various profiles by increasing the number of key times. The distance-based profile generator can remove the reference error This method increases the complexity of the generator and causes a discontinuous problem at changing from the time-based to the distance-based. To remove the reference error of the time-based profile generator for producing the trapezoidal profile, this paper proposes a novel profile generator based on a cascaded P-PI position controller. An unwanted velocity profile is generated from the difference between the deceleration ratio of the P-position controller and the dynamic range limiter. The proposed method can make the desired trapezoidal velocity profile with no position and reference error. The feasibility of the proposed profile generator is shown by several experimental results
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