Observer Design for a Variable Moment of Inertia System

Variable moment of inertia systems are common, and a popular laboratory system of this type is the “ball-and-beam”. Such systems are, however, nonlinear and often unstable. Efficient control requires full state information (or at least partial velocities), which are generally difficult to measure. That is why the design of state observers is a relevant problem. In this paper, a new design of an observer is proposed. This new nonlinear observer uses partial output injection and the circle criterion to ensure semiglobal stability. Moreover, we present a complete modeling of the system and systematic testing of the observer in comparison to a baseline in the form of a linear observer. The results show that the designed observer outperforms its linear counterpart and does not impede control.

A comparative study of performance of AC and DC electric drive control systems with variable moment of inertia

In electric drive control systems, the main goal is to maintain the driving motor speed to meet the mechanism’s requirements. In some practical industrial applications the mechanically-coupled load to the motor shaft has a varying mass during the system operation. Therefore, the change of mass changes the value of the moment of inertia of the system. The moment of inertia impacts the system operation, particularly the transient performance. Therefore, the variation of moment of inertia on the motor shaft during its operation creates additional challenges to accomplish a high-quality speed control. The main purpose of the current work is to study the impact of the variation of moment of inertia on the performance of both AC and DC electric drive control systems and to make a comparison between them. A mathematical analysis and simulations of the control system models had been presented; one time with three-phase induction motor and another time with DC motor, both with variable moment of inertia. A simulation of both systems had been accomplished using the Simulink software in MATLAB. The simulation results of operation of these systems have been analysed in order to get useful conclusions and recommendations for the electric drive control system designer.

Design and Analysis of a Variable Inertia Spatial Robotic Tail for Dynamic Stabilization

This paper presents the design of a four degree-of-freedom (DoF) spatial tail and demonstrates the dynamic stabilization of a bipedal robotic platform through a hardware-in-loop simulation. The proposed tail design features three active revolute joints with an active prismatic joint, the latter of which provides a variable moment of inertia. Real-time experimental results validate the derived mathematical model when compared to simulated reactive moment results, both obtained while executing a pre-determined trajectory. A 4-DoF tail prototype was constructed and the tail dynamics, in terms of reactive force and moments, were validated using a 6-axis load cell. The paper also presents a case study where a zero moment point (ZMP) placement-based trajectory planner, along with a model-based controller, was developed in order for the tail to stabilize a simulated unstable biped robot. The case study also demonstrates the capability of the motion planner and controller in reducing the system’s kinetic energy during periods of instability by maintaining ZMP within the support polygon of the host biped robot. Both experimental and simulation results show an improvement in the tail-generated reactive moments for robot stabilization through the inclusion of prismatic motion while executing complex trajectories.

Auto-Tuning Process of State Feedback Speed Controller Applied for Two-Mass System

The state feedback controller is increasingly applied in electrical drive systems due to robustness and good disturbance compensation, however its main drawback is related to complex and time consuming tuning process. It is particularly troublesome for designer, if the plant is compound, nonlinear elements are taken into account, measurement noise is considered, etc. In this paper the application of nature-inspired optimization algorithm to automatic tuning of state feedback speed controller (SFC) for two-mass system (TMS) is proposed. In order to obtain optimal coefficients of SFC, the Artificial Bee Colony algorithm (ABC) is used. The objective function is described and discussed in details. Comparison with analytical tuning method of SFC is also included. Additionally, the stability analysis for the control system, optimized using the ABC algorithm, is presented. Synthesis procedure of the controller is utilized in Matlab/Simulink from MathWorks. Next, obtained coefficients of the controller are examined on the laboratory stand, also with variable moment of inertia values, to indicate robustness of the controller with optimal coefficients.