Arun D Mahindrakar

A new strategy for the design of tracking control laws is presented for line-of-sight (LoS) pointing control of satellites that use only magnetorquers. This strategy makes use of the backstepping approach, and applies to satellites that require the LoS of a single instrument, such as a transmission antenna or camera, to be pointed at a given time, but not both simultaneously. Asymptotic stability of the desired trajectory is proved, provided the target pointing-direction lies outside some critical range. A control law so developed is numerically simulated for a nanosatellite mission scenario to demonstrate feasibility. © 2013 2013 California Institute of Technology.

We propose an output feedback second-order sliding mode controller to stabilize the cart on a beam system. A second-order sliding mode controller is designed using a Lyapunov function-based switching surface and finite-time controllers, while the state estimator is designed based on the Luenberger-like observer. The proposed observer extends the applicability of Luenberger-like observer to nonlinear systems that are not input-output linearizable, but can be approximately input-output linearized. The approximation is based on the physical property of the system, wherein certain terms in the total energy are neglected. Extensive numerical simulations validate the robustness of the proposed controller to parametric uncertainties using estimated states. © 2009 John Wiley & Sons, Ltd.

Map-making is a challenging task when the environment is unknown and the collected information is local. This paper presents the design of a hardware architecture for sensor-based map construction in a planar environment. In particular, the map is a Voronoi diagram of the environment. The Voronoi construction is based on a control law. Features of the proposed architecture are absence of arithmetic operations expensive in digital hardware and a planning algorithm for completing the map. Also, the implementation of control-law uses look-up tables and reuse of CORDIC module to avoid matrix multiplications. A highly area-efficient FPGA implementation of the architecture is also reported. Experiments with an FPGA-based robot confirm the effectiveness of the proposed approach.

This paper proposes a deterministic estimator for the estimation of the attitude of a rigid body. A deterministic estimator uses a minimal set of information and does not try to minimize a cost function or fit the measurements into a stochastic process. The proposed estimator obtains the attitude estimation utilizing only the properties of the rotational group SO(3). The information set required by the proposed estimator is a single vector information and rate gyro readings. For systems in which one of the rotational freedom is constrained, the proposed estimator provides an accurate estimate of the reduced attitude. The performance of the algorithm is verified on different experimental testbeds.

This paper deals with the stabilization of an under-actuated circular ball-and-beam system with constraints on the beam angle, ball traverse and the torque input. The constraints are formulated as a set of LMI's and a feedback control law is synthesized to maximize the basin of attraction of the unstable equilibrium. Simulation results are used to validate the proposed control strategy. © 2008 IEEE.

This paper presents a controller-design methodology for a class of underactuated mechanical systems that are affected by parametric uncertainties and external disturbances. The perturbations due to parametric uncertainties are mismatched, whereas those caused by external disturbances are of the matched type. Their effects are canceled by employing a novel strategy that combines time scaling and Lyapunov redesign. The control methodology is applied to a two-wheeled mobile inverted pendulum and a ball-beam system. Along the way, the nonexistence of a smooth control law for point-to-point stabilization of the mobile inverted pendulum is established. Simulation and experimental studies are used to verify the efficacy of the proposed controller-design method. © 2010 IEEE.

The Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) is a well-known method for control of complex physical systems in the port-Hamiltonian framework. Improvising on top of IDA-PBC which just focuses on stability, the memristive port-Hamiltonian control addresses performance concerns in the control task by providing a state-modulated damping term to IDA-PBC via a memristor element. The control way of implementing the memristive IDA-PBC first requires solving a set of Partial Differential Equations (PDEs) and then choosing a suitable memristance function for the system, out of which the former is a challenging math problem and the latter is a design problem. This paper employs reinforcement learning to learn the memristive IDA-PBC law and in the process, avoids the challenging task of solving PDEs, automates the design of the memristance function and also respects some physical system-level constraints which are not accounted for by the control way of solving IDA-PBC.

The mobile inverted pendulum (MIP) is a mechanical system that presents multiple control challenges. In particular, two objectives, namely desired position control and stabilization of the unstable pendulum-like central body, need to be simultaneously met. In this brief, we propose a novel smooth time-invariant controller to achieve the twin objectives. A feature of the controller design is that it readily extends to achieve waypoint tracking, another interesting task for mobile platforms. To validate the theory developed, an MIP has been indigenously designed and fabricated. Extensive experiments on the MIP have been performed. It has been observed that the system accomplishes position stabilization as well as waypoint tracking with negligible error.

In this brief, we design Lyapunov-based control laws to achieve two multi-objective tasks for a network of open-loop unstable, nonholonomic mobile inverted pendulum (MIP) robots, using a connected undirected graph for inter-agent communication. Using the first protocol, translationally invariant formations are achieved along with the synchronization of attitudes and heading velocities to desired values. Using the second protocol, the robots move into a formation and asymptotically track a trajectory. The control laws are based on the kinematic model of the mobile robot, and control torques for the MIPs are extracted using a two-loop control architecture. Both the protocols guarantee boundedness of the linear heading velocity, which is necessary for the stability of the two-loop control architecture. The proposed control laws are experimentally validated on indigenously built MIP robots.