Search

This research work presents the design of a position control algorithm for trajectory tracking of a four-degree-of-freedom robotic manipulator. The linkage mechanism of the manipulator is based on a parallelogram mechanism and in this manipulator, three parallelogram mechanisms are used. First, the CAD and the kinematic model of the manipulator are developed. The bond graph (BG) approach is applied to develop the dynamic model of the robotic arm based on kinematic equations. The BG model of parallelogram linkage is then compared with the Simulink model of parallelogram linkage and results are validated. Then, a position control algorithm is proposed to follow a set of trajectory planning applications. A GRBL-Arduino based controller is used to estimate the position of the end-effector as per the user's requirements. The simulation and experimentation work are performed for 3D trajectory tracking applications. The robotic arm is used for pick and place operation within the workspace.

This work describes design and implementation of a navigation and obstacle avoidance controller using fuzzy logic for four-wheel mobile robot. The main contribution of this paper can be summarized in the fact that single fuzzy logic controller can be used for navigation as well as obstacle avoidance (static, dynamic and both) for dynamic model of four-wheel mobile robot. The bond graph is used to develop the dynamic model of mobile robot and then it is converted into SIMULINKblock by using ‘S-function’ directly from SYMBOLS Shaktibond graph software library. The four-wheel mobile robot used in this work is equipped with DC motors, three ultrasonic sensors to measure the distance from the obstacles and optical encoders to provide the current position and speed. The three input membership functions (distance from target, angle and distance from obstacles) and two output membership functions (left wheel voltage and right wheel voltage) are considered in fuzzy logic controller. One hundred and sixty-two sets of rules are considered for motion control of the mobile robot. The different case studies are considered and are simulated using MATLAB-SIMULINKsoftware platform to evaluate the performance of the controller. Simulation results show the performances of the navigation and obstacle avoidance fuzzy controller in terms of minimum travelled path for various cases.

Some variation in the topological distribution of fibers inside the matrix phase of fiber reinforced polymers (FRP) is inevitable. Such irregularities can accelerate moisture diffusion and adversely affect the life of FRP. This paper presents a hierarchical technique for characterization of clustered microstructures and their transient moisture diffusion response. The clustering descriptors are derived for different fiber volume fractions (dilute to dense) for the quantitative definition of a given fiber matrix architecture. The metrics are normalized to remove dependence on volume fraction. The microstructures are analyzed for Fickian moisture diffusion. Suggested descriptors show a good correlation with transient diffusion response in relation to saturation time. The results can be used to predict the time-dependent moisture diffusion response of FRPs for any given fiber volume fraction.

The control of cardiovascular system by autonomic nervous system using model-based analysis is very useful to predict blood flow and blood pressure at different locations of human body. The regulation of cardiovascular system by autonomic nervous system is a very complex mechanism, so, an experimental-based model analysis may prove very helpful in studying and analysing its working properly. In this article, a very basic model of cardiovascular system is presented with blood pressure dynamics studied throughout the body. A new bond graph model of the autonomic nervous system embedded with baroreflex system is also presented. Autonomic regulation of ventricular contractility is represented by means of transfer functions. The results in terms of maximum ventricular elastance (Emax) and end systolic pressure are shown for two experiments. Another alternative modelling approach to represent the function of nervous system action in blood pressure regulation in terms of an overwhelming controller has been proposed. This controller overwhelms the system properties and therefore helps in managing the unmodelled parts or properties of a system and makes it impeccable for controlling complex systems. All the results and simulations are obtained using Symbols Shakti®software (Bond graph software).

Gas metal arc welding (GMAW) is extensively used for joining of different graded steels as well as aluminium and other nonferrous materials. GMAW offers clean welding with low defects without using flux and suitable for different positional welding. In the present work, a fabricated automatic movement setup is used for GMAW to study the influences of four different process parameters during joining of austenitic stainless steel AISI 316 using AISI 304 (ER304) filler wire. With this setup, welding is carried out maintaining a constant contact tube-to-workpiece (CTW) distance and uniform heat input. Experimental results and subsequent analysis show that the toughness is most significantly influenced by voltage followed by welding speed, gas flow rate, and current. Toughness reduces with the increase in shielding gas flow rate and welding speed as austenite and traces of retained delta ferrite may be present due to high solidification rate. Metallurgical observations by X-ray diffraction (XRD) and scanning electron microscopy indicate that solidification mode is mainly characterized by formation of fully austenite or austenite and ferrite at cell and dendritic boundaries. XRD results revealed that higher toughness is observed due to minimum formation of carbides.

This paper deals with the reconfiguration of an intelligent autonomous vehicle that utilizes an automatic navigation method and online supervision system and thus can be used to improve the safety, traffic management and space optimization inside the confined space of a port. The bond graph model of the vehicle’s dynamic system is developed in a modular and hierarchical modelling environment. An over-actuated intelligent autonomous vehicle with redundant actuators has four independent driven wheels, four independent braking wheels and a four-wheel steering system. This vehicle can be safely operated with appropriate control law restructuring even when some of its actuators are unusable due to a fault. For actuator fault detection, analytical redundancy relations, which are constraint relations that describe nominal system behaviour and are written in terms of the measured system variables, are derived from the bond graph model. Analytical redundancy relations are continuously evaluated to generate residual signals and the symptoms in these signals are monitored for actuator fault detection and isolation. Once one or more actuator faults are isolated, the system is reconfigured via the selection of an appropriate operating mode to prevent critical or accidental situations. This procedure is validated by considering a fault scenario with two reconfiguration options.

An overwhelming controller provides robustness against uncertain parameters, disturbances and un-modelled dynamics. A simplified inverse dynamics model is used in the present paper to develop an overwhelming controller for a parallel manipulator (a Stewart platform), where the controller accommodates modelling uncertainties such as the simplifications made for development of the inverse model in order to improve the computational efficiency. Such a control strategy leads to good trajectory tracking accuracy in the presence of unknown disturbances. However, in addition to trajectory tracking performance, the controller for a Stewart platform should also be able to control or limit the interaction forces in applications such as robot assisted surgery and low-impact docking. The environmental forces can be accommodated during the interaction period by modulating the impedance at the interface of manipulator and environment through virtual flexible foundations. The positional error induced during the force control phase can be recovered during the free flight or idle phase. While this approach has been used successfully in the past to control serial manipulators, the closed loop kinematic architecture in a parallel manipulator introduces many difficulties. This paper proposes a modified overwhelming control scheme for parallel manipulators with compensations for interaction force control and positional error recovery. Bond graph modelling is used as an integrated model and controller development tool. Force controlled machining on a spherical surface, which is akin to a surgical operation, is considered as an example application of the developed control strategy. The simulation results from the bond graph model of the controlled Stewart platform are presented to demonstrate the performance of the developed hybrid position force controller.

Stand–sit–stand (STS) motions are the most frequently performed activities of everyday life and require extensive movement of knee joint. People suffering from knee joint disorders face difficulties in performing this motion. The compact knee exoskeleton (KE) has proven to be a viable, less complex, and cheaper alternative to the available entire lower-, upper-, and full-body exoskeletons. With growing number of technical glitches and finite battery life problems, there exist risks of sudden failure of the actuator of KE that could be detrimental for the vulnerable users. To overcome this problem, there is a need to accommodate a backup actuator in KE which can continue providing assistance during movement if the primary actuator ceases to function. This article provides a performance comparison of a four-bar mechanism-driven KE that can accommodate both the linear and the rotary actuators. The modelling and simulation of the system are performed using the bond graph (BG) technique. The results successfully showed that both actuators offered desired ranges of motions needed for STS motion. Furthermore, the knee joint torques developed by the linear and rotary actuators were found to be 40 Nm and 57 Nm, respectively, which corresponds to 60% and 85% of the total torque required by the knee joint to perform STS motions, thereby reducing the user effort to 40% and 15%, respectively. Thus, both actuators are self-capable to provide necessary assistance at the knee joint even if the primary actuator ceases to work due to a sudden fault, the secondary actuator will provide the required rotation of the thigh link and will continue to deliver the assistive torque. The article also effectively shows the application of BG approach to model the multidisciplinary systems like KE as it conveniently models the system containing various elements in different energy domains.

This paper deals with the modelling and obstacle avoidance of a biped robot. At first, the bond graph-based three-dimensional model of the biped is proposed. The robot walking scheme depends upon the oscillating cylinder mechanism. Two DC motors are actuating the prismatic leg of the robot. Then, bond graph model is converted into the Simulinkblock which is further used for obstacle avoidance application. The physical model of the biped robot is also fabricated. The second part of the work deals with the development of the hybrid obstacle avoidance algorithm by using the merits of the line following, tangent bug and wall following algorithm. The practicability of algorithm is validated on two cases depend upon the positions of the obstacle. The coding of the algorithm is developed by using MATLABsoftware. The single rectangular shape obstacle is considered for obstacle avoidance by the robot during experimentation work. At last, the validation of the simulation and experimentation work is considered.