Proportional control

About: Proportional control is a research topic. Over the lifetime, 3756 publications have been published within this topic receiving 49050 citations.

Nonlinear Control Analysis of a Double-Gimbal Variable-Speed Control Moment Gyroscope

Abstract: A single double-gimbal variable-speed controlmoment gyroscope is considered as amethod for three-dimensional spacecraft attitude control. First, the system’s equations of motion are developed, where gimbal and wheel accelerations are prescribed as control inputs. The resulting necessary motor torques as well as system energy rates are computed for verification. Next, a novel control algorithm is developed from the stability constraint for reference trajectory tracking. In contrast with the control development for single-gimbal variable-speed gyros, a Newton–Raphson scheme is required to solve for the desired double-gimbal variable-speed control moment gyroscope control variables because they appear in cross product and quadratic form, preventing analytical solutions. Analysis of the control theory suggests that the same torque amplification effects exist as in a single-gimbal control moment gyro, but control by a single double-gimbal variable-speed control moment gyroscope device is not robust due to potential configurations that result in control singularities. When these singularities are avoided, a simulation with successful reference trajectory tracking is achieved. Allowing double-gimbal gyros to have variable wheel speeds provides additional torquing capabilities, which is significant if failure modes are considered. As will be shown, a single double-gimbal variable-speed control moment gyroscope device can provide limited threedimensional attitude control.

Discrete-Time Sliding Mode Control With Time-Varying Surface for Hard Disk Drives

Abstract: A time optimal-based discrete-time sliding mode control (DSMC) scheme with application to hard disk drives (HDDs) is developed in this study. In this approach, an approximate time optimal switching curve is adopted for the time-varying sliding mode design and the controller, which consists of an equivalent part and a discontinuous one, is designed such that the trajectory from any initial point is driven into a sliding region in the vicinity of the switching surface without chattering and thereafter remains inside it. By using the time-varying switching surface, one unified framework for both track seeking and following control is provided and smooth transition from seeking control to track following control is achieved as well. Simulation and experimental studies on the design of controller in HDDs were conducted to illustrate its feasibility and effectiveness. The simulation/experimental results demonstrate that the proposed scheme provides better performance during track seeking than the commonly used discrete-time proximate time-optimal servomechanism (PTOS) and sliding mode proximate time optimal servomechanism (SMPTOS). Moreover, the unified controller achieves better disturbance suppression in track-following than the proportional-integral-differential (PID) control.

A PD-type regulator with exact gravity cancellation for robots with flexible joints

Abstract: We present a new control approach to regulation tasks for robots with elastic joints in the presence of gravity. The control law combines a term that cancels the gravity effects on the robot link dynamics with a PD-type error feedback on the motor variables. The first control component follows from the feedback equivalence principle when imposing to the link variables the same dynamic behavior as if gravity were absent. The PD component can then be designed in a rather straightforward way. Global asymptotic stability is shown via Lyapunov analysis, without the need of strictly positive lower bounds neither on the proportional control gain nor on the structural joint stiffness. The control approach is also extended to the case of robot joints with nonlinear stiffness.

A rule-based adaptive PID controller

Abstract: The authors describe a functioning expert controller implemented with industrial programmable logic controller technology. In its present state the controller implements an adaptive PID (proportional, integral, and derivative) algorithm based on rule-based logical modules. The controller does not presume a model for the system. It detects several features of the current system response to a step input change and uses a pattern matching procedure to adjust the PID parameters to reshape the system output response. >