Tarun Kumar Bera

Evaluation of antilock braking system with an integrated model of full vehicle system dynamics

Abstract Antilock braking system (ABS), traction control system, etc. are used in modern automobiles for enhanced safety and reliability. Autonomous ABS system can take over the traction control of the vehicle either completely or partially. An antilock braking system using an on–off control strategy to maintain the wheel slip within a predefined range is studied here. The controller design needs integration with the vehicle dynamics model. A single wheel or a bicycle vehicle model considers only constant normal loading on the wheels. On the other hand, a four wheel vehicle model that accounts for dynamic normal loading on the wheels and generates correct lateral forces is suitable for reliable brake system design. This paper describes an integrated vehicle braking system dynamics and control modeling procedure for a four wheel vehicle. The vehicle system comprises several energy domains. The interdisciplinary modeling technique called bond graph is used to integrate models in different energy domains and control systems. The bond graph model of the integrated vehicle dynamic system is developed in a modular and hierarchical modeling environment and is simulated to evaluate the performance of the ABS system under various operating conditions.

Bond graph model-based evaluation of a sliding mode controller for a combined regenerative and antilock braking system

Combined regenerative and antilock braking in electric/hybrid-electric vehicles provides higher safety in addition to an energy storing capability. Development of a control law for this type of braking system is a challenging task. The antilock braking system (ABS) uses a control strategy to maintain the wheel slip within a predefined range. A sliding mode controller (SMC) for ABS is developed to maintain the optimal slip value. The braking of the vehicle, performed by using both regenerative and antilock braking, is based on an algorithm that decides how to distribute the braking force between the regenerative braking and the antilock braking in emergency/panic braking situations as well as in normal city driving conditions. Detailed bond graph models of a quarter car and four-wheeled vehicles are used in this article to implement and test the control laws. It is found that with combined regenerative and antilock braking, the vehicle’s safety increases (in terms of stopping distance and manoeuvrability) and some amount of kinetic energy can be recovered and stored in the regenerative battery pack. The passenger comfort is improved when a sliding mode ABS controller is used in place of a standard ABS controller for the mechanical braking part. Moreover, the influence of load transfer on the wheels during braking was evaluated on a four-wheeled vehicle model.

Influence of Current and Shielding Gas in TiO2 Flux Activated TIG Welding on Different Graded Steels

In tungsten inert gas (TIG) welding, limited depth of penetration can be achieved during single pass welding. To achieve the desired depth of penetration, the speed of welding needs to be significantly reduced and hence, the productivity decreases. In the present work, the effect of TiO2 activated flux on penetration is evaluated for different workpieces namely AISI 1020, AISI 304, AISI 316, and Duplex 2205 steels at different currents and shielding gas compositions. The results show a significant increase in the depth of penetration and reduction in the width-to-penetration ratio using the activated flux for all the workpiece materials considered here. Current increases the depth of penetration, however, the influence of flux becomes more significant with higher welding current. Maximum of 37.8%, 44.3%, 47%, and 124% increase in depths of penetration is measured for AISI 1020, AISI 304, AISI 316, and Duplex 2205 steels, respectively, when activated flux is used. Also, maximum of 70% increase in the depth of penetration is further achieved when Ar along with 5% H2 is used as the shielding gas compared to that when pure Ar is used. The constriction of arc column increases the energy density, which increases the depth of penetration. Measurement of microhardness and metallurgical observations are carried out for samples after TIG welding and activated tungsten inert gas (ATIG) welding and compared to observe the solidification phenomenon during the process.

Mechanical and Metallurgical Studies in Double Shielded GMAW of Dissimilar Stainless Steels

In the present work, a simple arrangement is made to provide double layer shielding gas supply in addition to primary shielding during gas metal arc welding (GMAW) of two dissimilar stainless steels, i.e., AISI 316 and duplex 2205. Influences of double layer shielding in addition to five more process parameters like welding current, voltage, material of the electrode wire, the type of primary shielding gas, and flow rate on joint tensile strength and fusion zone microhardness are studied. An experimental design technique is used to design the experimental conditions and the results are analyzed to observe the influences of each process parameter and their interactions. The tensile strength is more influenced by the electrode material and the type of shielding, whereas current, interaction between current × voltage and current × flow rate significantly influence microhardness. Welding voltage influences both tensile strength and microhardness. Double layer shielding with CO2 as an outer shielding layer helps in controlling the cooling rate which improves the tensile strength and microhardness. Microstructural observations by scanning electron microscopy reveal that moderate to low heat input with a single layer of shielding results in poor joint strength and severe damage or lack of fusion, and the duplex 2205 filler gives the maximum joint strength due to the presence of a ferrite structure.

Robust overwhelming control of a hydraulically driven three-degrees-of-freedom parallel manipulator through a simplified fast inverse model

Abstract An overwhelming controller-based implicit system inversion scheme is proposed in this work to control a hydraulically driven planar (three-degrees-of-freedom) parallel manipulator. The physical model-based design of the controller is developed by using bond graphs. The electro-hydraulic actuator in the leg is modelled by including the dynamics of the servo-valve and the cylinder. A leg-space force-feedback controller is proposed for controlling the hydraulic pressures acting on the pistons of the actuators. The objective is to develop a fast inverse model which is suitable for real-time implementation in the controller. It is shown that an approximate inverse model which correctly represents the kinematics of motion but has incorrect representation of inertias is sufficient for the controller design because of the high feedback gains used in the overwhelming control strategy. This controller, based on the approximate simple inverse model, generates the right driving forces for the actual system whose model is much more complicated and uncertain. Finally, the controller design for a planar vehicle simulator is considered as an example and the corresponding simulation results are used to validate the robustness of the model-based overwhelming controller to the modelling uncertainties.

Force control in a parallel manipulator through virtual foundations

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.

Design and validation of a reconfiguration strategy for a redundantly actuated intelligent autonomous vehicle

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.

Influence of Heat Input in Automatic GMAW: Penetration Prediction and Microstructural Observation

In the present work, the influence of heat input is studied on depth of penetration while depositing bead on AISI 304 stainless steel using an indigenously fabricated automatic gas metal arc welding (GMAW) movement setup. Depth of penetration and fusion zone profiles are predicted at different conditions by the bond graph modeling approach and validated using measured depth of penetration and fusion profile. The effects of heat input on toughness and metallurgical behavior are analyzed while joining AISI 304 plates using automatic GMAW. Heat input and gas flow rate significantly influence the toughness at room temperature and at −20°C. Metallurgical observations by scanning electron microscopy are carried out and it is observed that high heat input and lower cooling rate increase grain size. High heat input and rapid cooling prevent grain growth and lead to grain refinement.

BOND GRAPH MODEL-BASED INVERSION OF PLANAR PARALLEL MANIPULATOR SYSTEMS

Abstract Overwhelming controllers have been successfully used in the past for trajectory and impedance control. An overwhelming controller uses an image or copy of the system model in the model-based controller. This model represents the kinematic constraints for implicit system inversion. The controller output is used to actuate the controlled system through a high feedback gain, which ensures that the dynamics of the controller overwhelms the plant dynamics. The overwhelming controller implementation for a serial robotic system is a straightforward task. However, implementation of a bond graph model-based overwhelming controller for a parallel manipulator shows up a few difficult causal loops. Removal of these causal loops and a few other subtle modifications yield a computationally efficient inverse model for real-time implementation. As validation of the developed approach, trajectory tracking in constrained planar welding operation is considered. The corresponding simulation results are presented.

Bond graph aided thermal modelling of twin-tube shock absorber

Abstract Keeping in view the role of heat generation and dissipation, the aim of this work is to develop a thermal model for the twin-tube hydraulic shock absorber using bond graph approach. In this paper, experiment is also conducted on a rear shock absorber of a commercial passenger sedan. The temperature at the upper and lower part of the shock absorber and the force applied on the shock absorber are measured. Simulation results are compared with the experimental results to validate the model. Both the experimental and simulation results show that the volume flow rate of hydraulic fluid is more in the upper chamber than that in the lower chamber. If the surface temperature and hydraulic fluid temperature become equal, external work given to the shock absorber acts as a single entity transferring heat to the surroundings. This point marks the point of maximum heat transfer to the surroundings.