Ranjit Kumar Barai

An FPGA based implementation of a flexible digital PID controller for a motion control system

Implementation of digital controllers in embedded environment suffers from the inherent problems associated with analog-digital signals interfacing in hard real-time, therefore, the control algorithms are invariantly subjected to approximations. This paper presents a novel technique for implementation of an efficient FPGA based digital Proportional-Integral-Derivative (PID) controller for the motion control of a permanent magnet DC motor. The implementation technique circumnavigates the problem of interfacing analog and digital systems in real-time. The controller is used in a speed control loop. The hardware implementation has been done on a Xilinx Spartan 3 FPGA chip. A novel technique has been adopted for the generation of the control input as a PWM signal for controlling the motor driver circuit and decoding the optical encoder data for using it for the speed feedback in the PID control loop. The VHDL algorithm for the proposed implementation has also been presented in this paper. A comparison of the experimental results with the Matlab® based simulation shows the effectiveness of the proposed method.

Nonlinear state feedback controller design for underactuated mechanical system: A modified block backstepping approach

This paper presents the formulation of a novel block-backstepping based control algorithm to address the stabilization problem for a generalized nonlinear underactuated mechanical system. For the convenience of compact design, first, the state model of the underactuated system has been converted into the block-strict feedback form. Next, we have incorporated backstepping control action to derive the expression of the control input for the generic nonlinear underactuated system. The proposed block backstepping technique has further been enriched by incorporating an integral action additionally for enhancing the steady state performance of the overall system. Asymptotic stability of the overall system has been analyzed using Lyapunov stability criteria. Subsequently, the stability of the zero dynamics has also been analyzed to ensure the global asymptotic stability of the entire nonlinear system at its desired equilibrium point. The proposed control algorithm has been applied for the stabilization of a benchmarked underactuated mechanical system to verify the effectiveness of the proposed control law in real-time environment.

Autonomous robot coverage in rescue operation

Mobile robots are integrated into a search and rescue team as tools for searching victims in dangerous areas that is harmful for human, so as to follow the human entity during the mission. Generalized Local Voronoi Diagram (GLVD) algorithm is introduced to model the area, coverage and cooperation. The senor based motion planning is implemented on the robots for navigation of the area and coverage. The focus here is on the rescue of entities present following area coverage. A brief description of the on-going research and the results obtained is also provided.

Path planning of autonomous mobile robot: A new approach

In this present work, we present an algorithm for path planning to a target for mobile robot in unknown environment. The proposed algorithm allows a mobile robot to navigate through static obstacles and finding the path in order to reach the target without collision. This algorithm provides the robot the possibility to move from the initial position to the final position (target). The proposed path finding strategy is designed in a grid-map form of an unknown environment with static unknown obstacles. The robot moves within the unknown environment by sensing and avoiding the obstacles coming across its way towards the target. When the mission is executed, it is necessary to plan an optimal or feasible path for itself avoiding obstructions in its way and minimizing a cost such as time, energy and distance. The proposed path planning must make the robot able to achieve these tasks: to avoid obstacles and to make ones way toward its target. The algorithms are implemented in Matlab, afterwards tested with Matlab GUI; whereby the environment is studied in a two dimensional coordinate system. The simulation part is an approach to the real expected result; this part is done using Matlab to recognize all objects within the environment and since it is suitable for graphic problems. Taking the segmented environment issued from Matlab development, the algorithm permit the robot to move from the initial position to the desired position following an estimated trajectory using Maps in Matlab GUI.

Global stabilization of a flat underactuated inertia wheel: A block backstepping approach

This paper presents the formulation of a novel block-backstepping based control algorithm to address the global stabilization problem of a flat underactuated inertia wheel system. The ideas behind the method are as follows. At first, state model of the inertia wheel system has been converted into block-strict feedback form. Then the control Lyapunov function has been designed for each cascaded dynamic block to derive the expression of the control input for the overall nonlinear system. The overall asymptotic stability of the inertia wheel system has been analyzed using Lyapunov Stability Criteria. Finally, the effectiveness of the proposed control algorithm has been verified in the simulation environment.

Block Backstepping Design of Nonlinear State Feedback Control Law for Underactuated Mechanical Systems

This book presents a novel, generalized approach to the design of nonlinear state feedback control laws for a large class of underactuated mechanical systems based on application of the block backstepping method. The control law proposed here is robust against the effects of model uncertainty in dynamic and steady-state performance and addresses the issue of asymptotic stabilization for the class of underactuated mechanical systems. An underactuated system is defined as one for which the dimension of space spanned by the configuration vector is greater than that of the space spanned by the control variables. Control problems concerning underactuated systems currently represent an active field of research due to their broad range of applications in robotics, aerospace, and marine contexts. The book derives a generalized theory of block backstepping control design for underactuated mechanical systems, and examines several case studies that cover interesting examples of underactuated mechanical systems. The mathematical derivations are described using well-known notations and simple algebra, without the need for any special previous background in higher mathematics. The chapters are lucidly described in a systematic manner, starting with control system preliminaries and moving on to a generalized description of the block backstepping method, before turning to several case studies. Simulation and experimental results are also provided to aid in reader comprehension.

Stabilization of Furuta Pendulum: A backstepping based hierarchical sliding Mode approach with disturbance estimation

An adaptive backstepping sliding mode controller, which combines both the merits of adaptive backstepping control and sliding mode control, is proposed to address the control problem of the Furuta Pendulum in the presence of external disturbances. At first, the underactuated state model of the Furuta Pendulum has been divided into two separate subsystems. Then a pair of first layer sliding surfaces is defined for each second-order subsystem. Two separate adaptive backstepping based control law is designed for each of the subsystem to ensure the states of each subsystem approach to their own sliding mode surface. Based on this two first layer sliding surfaces, a second layer sliding surface is defined correspondingly, through which a total control law is derivedto make sure that all states can converge to their desired value via Lyapunov stability theorem. The asymptotic stability of all the sliding surfaces has proven theoretically, and simulation results show the controllers validity and its adaptive abilities for all kinds of extraneous disturbances.

Kinematics, Navigation, and Path Planning of Hexapod Robot

In Chap. 3, fundamental analysis on COMET-IV’s leg kinematics and dynamics has been briefly discussed. On further research progress on this robot, the developed kinematics and dynamics are exploited to be used for end-effector force on foot detection and overall COMET-IV stability for force-attitude control purposes. In COMET-IV research progress, the total force on foot is calculated for center of mass (CoM) identification as an input for robot attitude during walking session. This method is based on shoulder coordination system (SCS) kinematics on vertical position and total of force on foot for each touching leg on the ground. On the other hand, the designed force delivery on foot value is categorized phase by phase and threshold sensing method is applied for dynamic trajectory walking named force threshold-based trajectory. This method is done to achieve the novel end-effector force sensorless method that is applicable for large-scale legged robot that required expensive sensor on each leg’s tip.

Sliding mode compensation of inverse dynamics velocity control

Direct drive manipulators operate at high speeds, because the reduction gears are eliminated for accurate positioning of the end effector. Obviously, inverse dynamics velocity control is a suitable choice for the control of direct drive manipulator to tackle the dynamic effects due to its high speed operation. However, uncertainty in the dynamic model, and also in the inverse dynamic model, of the manipulator deteriorates its tracking performance. This paper presents a novel approach of inverse dynamics velocity control of direct drive manipulator based on sliding mode compensation technique. The compensated inverse dynamics velocity control scheme is robust against the ill-effects of the model uncertainties and exhibits robust tracking performance of the desired velocity trajectories in the robot joint space. Moreover, the proposed inverse dynamic controller can be designed based on the nominal dynamic model, thus eliminating the need for the online calculation of the computation intensive time varying parameters of the robot dynamic model. The effectiveness of the proposed control algorithm has been validated in the simulation considering a 3 DOF direct drive manipulator model.

Reference input tracking of inversion-based non-minimum phase system using adaptive two-degree-of-freedom control

Reference input tracking plays a major role in control system Engineering. Inverse model technique is very useful for exact tracking of minimum phase system but for non-minimum phase system, it gives unbounded output response. This paper proposes an effective method for achieving the approximate desired trajectory tracking of unstable inversion-based non-minimum phase (NMP) system. Here two-degree-of-freedom control theory has been applied where feedback control is provided by arbitrary pole placement method to create the bounded response of unstable NMP system. Lyapunov based Direct Model Reference Adaptive Control (MRAC) of inverse transfer function model of NMP system act as feed-forward compensator in 2DOF framework to track the reference input trajectory. Unstable non-minimum phase plant can successfully track step, ramp and parabolic input signal with a minimum steady state error shown in the simulation results. Initial undershoot which is obvious in NMP system has been completely removed by this control strategy.