High altitude electromagnetic pulses (HEMPs) and solar-geomagnetic disturbances (GMDs) both have the potential to impact the reliable operation of the electric power grid. GMDs, and the low-frequency portion of HEMP insults, introduce currents into the grid that can result in the magnetic cores of large power transformers becoming saturated. This paper presents a novel approach to HEMP/GMD mitigation, wherein actively controlled voltage sources are utilized to nullify a low frequency EMP insult. This method is evaluated on several power system case studies, including a single transformer system, a 20-bus system, and a 150-bus system. Results show that the active mitigation is able to successfully prevent transformer saturation in all cases.

This paper develops a novel control system design methodology that uniquely combines: concepts from thermodynamic exergy and entropy; Hamiltonian systems; Lyapunov's direct method and Lyapunov optimal analysis; electric AC power concepts; and power flow analysis. Relationships are derived between exergy/entropy and Lyapunov optimal functions for Hamiltonian systems. The methodology is demonstrated with a few fundamental numerical simulation examples: 1) a Duffing oscillator/Coulomb friction nonlinear model that employs PID regulator control; and 2) a linear PID tracking servo control design for a translational single robot link system. The control system performances are partitioned and evaluated based on exergy generation and exergy dissipation terms. This novel nonlinear control methodology results in both necessary and sufficient conditions for stability of nonlinear systems

An optimized path-planning approach is presented for flexible dynamic systems. Feedforward command profiles are determined for rest-to-rest large angle maneuvers that keep vibrations to a minimum. The performance index included both minimum energy and minimum time optimization problems. The feedfoward command profiles were generated by solving a discrete-time optimal control problem via discrete dynamic programming (DDP). A simple planar two-link flexible robot arm was utilized to demonstrate the DDP path-planning scheme. Numerical simulation results included: 1) minimum effort, 2) minimum effort with bounds, 3) minimum time, and 4) minimum torque-rate or power, respectively. The DDP approach demonstrated an effective alternative for numerical optimization, to generate optimal feedforward trajectory profiles.

This paper introduces a robust adaptive control architecture for nonholonomic mobile robots. The concept of backstepping provides a bridge between the kinematics and dynamics. In previous work normally only the vehicle steering, dependent upon the kinematics are considered for vehicle control. Improved tracking performance is achieved by including vehicle dynamics and robustness compensation for variances in parameters. Numerical simulations demonstrate the effectiveness of the robust adaptive control algorithm.

We present an output feedback sliding mode control (OFSMC) architecture for slewing flexible joint and link robot structures. A decoupled two-channel OFSMC is used to servo the flexible structure and suppress residual vibrations. A separate sliding surface is specified for each channel. The results of this study include the analytical dynamic and control system development with experimental verification. The control algorithm uses the output sensor data from the encoder and strain sensor along with filters to derive velocity information to compute the control effort for the motor and strain actuators. Near-minimum time maneuvers based on an equivalent rigid structure are used to slew the flexible active structure. The tip mass was varied to evaluate control system robustness. Experimental slewing studies were performed to compare the benefits of using active rather than passive structures. In addition, the OFSMC was compared against a conventional PID controller. For the active case the experimental results showed a reduction in residual vibration and settling time.

This paper evaluates three model reference adaptive control (MRAC) schemes for completing a telerobotic task. The three proposed schemes are evaluated for accurate trajectory control of a general three-degree-of-freedom robotic manipulator, in the presence of large payload variations, and modeling inaccuracies. The three MRAC schemes evaluated are: (1) Computed-torque method, which uses the nonlinear dynamic model of the robot in the control formulation and Popov's hyperstability criteria, (2) independent joint control method, which uses decoupled linear dynamic equations in the control formulation and based on Popov's hyperstability criteria, and (3) independent joint control method based on sensitivity analysis. Computer simulations of a three-degree-of-freedom manipulator, with a large payload and fast maneuver are used to analyze the performance of the three schemes. The investigation shows the robustness of the computed-torque method when compared to the independent joint schemes.