Design method of I-PD force control system based on instantaneous state observer for industrial robot

So far, a considerable amount of research has been devoted to flexible arms, especially to their modelling, position control and vibration control. Meanwhile very few research has addressed the problem of force control, since it is one of the most important functions of the robot tasks. In this paper, we present a two-degree-of-freedom control system for the force control of flexible cartesian robots. Use of a two-degree-of freedom control system guarantees the independent design of the feedforward and feedback control characteristics. The feedforward controller is designed using inverse dynamics, while the design of the stabilized feedback controller is achieved by Lyapunov's direct method. Numerical simulation and experimental results confirm that faster precise force control can be realized with the proposed control system.

A networked control system (NCS) is one in which controller(s), actuator(s),and sensor(s)exchange command signals and data through a limited-bandwidth communication network that may be used by other applications, devices, and control systems. Compared to classical wired controlled systems, NCSs possess many advantages. In this paper, we propose the modeling and networked control of two-rigid link robot arm. To deal with the time delays that may occur during communication between the components of the system through the network, a model of the system was first determined, and second, PID controllers were designed based on the obtained model and using the stability region boundary locus technique. To demonstrate the validity of the proposed approach, numerical simulations were conducted using TrueTime, Simscape, SimMechanics, and Simulink with the MATLAB environment

Importance of Polynomial in Coefficient Diagram Method

This paper presents a high-performance and simple guidance method for a short-range missile. Missile control systems are designed along the estimated flight envelope of the missile based on coefficient diagram method. The linear time invariant (LTI) models are obtained by linearizing missile nonlinear model at specific operating points. The governing equations of motion are accurately modeled by taking into account the effect of the mass rate and the center of gravity shift. A novel algebraic approach called coefficient diagram method (CDM) is used to design normal acceleration and roll angle control systems. The proportional navigation law is considered as the guidance law. One case of engagement scenarios is studied and the missile performance is evaluated. The robustness of the proposed controller is tested against parameter uncertainties and wind disturbance.

Inherent compliance equips soft robotic arms with such advantages as incomparable flexibility, good adaptability, and safe interaction with the environment, etc. However, the strong nonlinearity also brings challenges to predict their dynamic behaviors. This work presents a simplified dynamic model of an underwater soft robotic arm which has three fiber-reinforced hydraulic chambers distributed symmetrically in each section. By controlling the pressures in the chambers, the soft robotic arm can perform complex spatial motion with multiple degrees of freedom. The model is based on Lagrangian method and piecewise constant curvature hypothesis, and considers the nonlinear viscoelasticity of soft material. The model accuracy is verified by the experiments of a two-section soft robotic arm with different actuation modes. The effects of geometrical features on dynamic response are also investigated through model-based simulation and test verification, which can provide guidance to parameter optimization. The proposed dynamic model can be extended to multiple sections and contribute to behavior analysis, performance prediction, and motion control of the soft robotic arm.

Modelling and Control of an Elastic Robot Arm with Rotary and Prismatic Joints

<p>The accelerated growth of an increasingly automated industry requires the use of autonomous robotic systems. However, the use of these systems commonly requires an enormous amount of sensors. In this paper we evaluate the performance of a new system for visual control of a selective compliance assembly robot arm (SCARA) robotic arm using a monocular depth map that only requires one monocular camera. This system aims to be an efficient alternative to reduce the number of sensors in the robotic arm area while maintaining the effectiveness of traditional vision algorithms that use stereoscopic architectures of cameras. For this purpose, this system is compared with representative state-of the-art vision algorithms focused on the control of robotic arms. The results are statistically analyzed, indicating that the algorithm proposed in this research has competitive performance compared to state-of-the-art robotic arm visual control algorithms only using a single monocular camera.</p>

Mitigating collision is a fundamental issue in contact problems, and is required to ensure the safety of a robotic cell. Research into the contact problem between robots and their environment is divided into two parts: one uses the environmental contact model and parameter estimation, the other uses the robot force control method. There are two main problems with this research method. One is that the two research levels are not effectively combined to form a complete solution for force control in practice. The other problem is that research on excessive contact force in the collision phase has not been studied in depth for force control. In this paper, a sensing-executing bionic system is proposed that combines environmental detection and robotic force control based on the way an ant functions. The bionic system clearly explains the process from environment detection to robot control, which can provide guidance when designing a new robot control system. An adaptive switching control algorithm is proposed to mitigate the collision force in the collision phase. From the simulation results, the collision force is significantly reduced due to the implementation of adaptive switching control. Finally, a new self-sensing device is designed which can be integrated into the robot control device. However, as there are no additional sensors or computational complexity in the system, the effectiveness of the circuit and superiority of the adaptive parameter update must be verified by experimentation.

In this paper, an H∞ direct output feedback control algorithm through minimizing the entropy, a performance index measuring the tradeoff between H∞ optimality and H2 optimality, is employed to design the control system in reducing structural responses due to dynamic loads such as earthquakes. The control forces are obtained from the multiplication of direct output measurements by a pre-calculated time-invariant feedback gain matrix. To achieve optimal control performance, the strategy to select both control parameters γ and α is extensively investigated. The decrease of γ or increase of α results in better control effectiveness, but larger control force requirement. For a single degree-of-freedom (SDOF) damped structure, exact solutions of output feedback gains and control parameters are derived. It can be proved analytically that the LQR control is a special case of the proposed H∞ control. Direct velocity feedback control is effective in reducing structural responses with very small number of sensors and controllers compared with the DOFs of the structure. In active control of a real structure, control force execution time delay cannot be avoided. Relatively small delay time not only can render the control ineffective, but also may cause system instability. In this study, explicit formulas to calculate maximum allowable delay time and critical control parameters are derived for the design of a stable control system. Some solutions are also proposed to increase the maximum allowable delay time.

This paper presents engine piston installation using industrial robots. Because the current manual and hard automation engine piston installation systems are either labour intensive or inflexible and costly, the three-robot and two-robot piston installation systems are developed and investigated. The robotic piston installation process is simulated. A robotic piston stuffing gripper with ring detection is designed to perform the sophisticated stuffing process. Robot force control is used in the cylinder bore finding. The piston stuffing is implemented using a search-finding method based on the force control. The searching method and parameters are discussed. Related future research and development are proposed.

The KEKB project, constructing an asymmetric electron-positron collider for B physics in Japan, has officially approved and has started in 1994. The goal of the KEKB accelerator control system is to provide a powerful, flexible, and extendible control system for both accelerator physicists, who need beam information and are not so patient, and operators, who control all equipment. To achieve this goal on schedule, we decided to use standard technology where it is applicable. We have studied some existing control systems based on Standard Model of the modern accelerator control systems, such as EPICS or V-system, as a framework of the control system and have chosen the base of the control system according to this study. Another key issue in the KEKB accelerator control system is use of database management system for unified management of the information which the control system requires. Integration of control system with the modeling software, SAD, is also discussed.

The purpose of this paper is to present our results in developing a dynamic model of the Mitsubishi PA-10 robot arm for the purpose of low velocity trajectory tracking using low feedback gains. The PA-10 is ideal for precise manipulation tasks due to the backdrivability, precise positioning capabilities, and zero backlash afforded by its harmonic drive transmission (HDT). However, the compliance and oscillations inherent in harmonic drive systems, and the lack of any technical information on the internal dynamics of the transmission, make the development of an accurate dynamic model of the robot extremely challenging. The novelty of this research is therefore the development of a systematic algorithm to extract the model parameters of a harmonic drive transmission in the robot arm to facilitate model-based control. We have modeled all 7 joints of the Mitsubishi PA-10, and we have done several experiments to identify the various parameters of the harmonic drive system. We conclude with a sample trajectory tracking task which demonstrates our model-based controller for the Mitsubishi PA-10 robot arm.

Planar soft space robotic manipulators: Dynamic modeling and control

The purpose of this study is to control simultaneously, motion and vibration of flexible 2-link robot arms. For this purpose, we had used modeling method called an 'extended reduced-order physical model (extended model)' to make a model of one-link flexible robot arm. The model of the flexible 2-link robot arms is made of a combination of the model of each link that is regarded as one link flexible robot arm. To connect each link, the constraint addition method is used. This is creating method of an equation of motion in multi-body systems. It is verified that the results of the simulation are effective for control of flexible 2-link robot arms.

This paper introduces a modular prototyping system architecture that allows for the modeling, simulation and control of different maritime cranes or robotic arms with different kinematic structures and degrees of freedom using the Bond Graph Method. The resulting models are simulated in a virtual environment and controlled using the same input haptic device, which also provides the user with a valuable force feedback. The arm joint angles can be calculated at runtime according to the specific model of the robot to be controlled. The idea is to develop a library of crane beams, joints and actuator models that can be used as modules for simulating different cranes. The base module of this architecture is the crane beam model. Using different joint modules to connect several such models, different crane prototypes can be easily built. The library also includes a simplified model of a vessel to which the crane models can be connected in order to get a complete model. Related simulations were carried out using the so-called 20-sim simulator to validate efficiency and flexibility of the proposed architecture. In particular, a two-beam crane model connected to a simplified vessel model was implemented. To control the arm, an omega.7 from Force Dimension was used as an input haptic device.