Lyapunov-based control design for multiple robots handling a common object

In this article, we address the problem of controlling multiple robots manipulating a rigid object cooperatively. First we propose and prove a few fundamental properties of the multirobot dynamical system. These properties are then exploited to design aset point regulation controller. The proposed controller takes into account the dynamics of both the object and the manipulators. This controller enables us to control the position of the object and the internal forces acting on the object. An adaptive version of the proposed controller is then introduced. The adaptive controller is able to account for the uncertainty in the mass of the load while ensuring the asymptotic convergence of the load position and the internal forces to their desired values.     

A new minimum-time control law for a one-mode model of a flexibleslewing structure

The construction of a minimum-time control law for a single-axis, undamped, one-mode model of a flexible slewing structure is described. The set of necessary and sufficient conditions for optimality is developed using phase-plane techniques, and is given in terms of the vibration frequencies and the rigid-body states. This effectively provides the switching hypersurface in four-dimensional space. The resulting control strategy can be implemented on line since no a priori computation of switching times is required     

Modeling of multiple mobile manipulators handling a common deformable object

The dynamic equations of motion for a system of multiple mobile manipulators carrying a common deformable object are developed. The derived centralized model is based on Kane's approach to dynamics. The imposed kinematic nonholonomic constraints are included and incorporated into the dynamics. It is pointed out, however, that these kinematic constraints are only necessary, and they only become sufficient to impose nonholonomic motion when accompanied by the dynamic counterparts. Sufficient conditions for avoiding tipping over by the mechanisms are also provided. The whole set of constraint equations is analyzed and useful properties for the set of admissible solutions for the ground reaction forces are obtained. The deformable object under manipulation is modeled and the simplest approximating grid structure is indicated. © 1998 John Wiley & Sons, Inc.     

Addendum to “A new minimum-time control law for a one-modemodel of a flexible slewing structure”

In a previous article by Barbieri et al. (ibid., vol.38, p.142-6 (1993)) a set of five conditions were given to characterize the switching hypersurface of the minimum-time, single-axis controller for an undamped, one-mode model of a flexible slewing structure. The purpose of this paper is to show that the five conditions have been found to be reducible to three. This oversight is repaired, and a new plot of the three conditions in a two-dimensional plane is isolated to easily identify the switching strategy in real-time     

A self-adjusting active compliance controller for multiple robots handling an object

This paper presents the concept and experimental validation of a self-adjusting active compliance controller for n robots handling its compliant behaviour concerning partly unknown flexible object. The control strategy is based on the decomposition of the 6n-dimensional position/force space and includes a feedforward and feedback level. The feedforward level contains motion coordination, force distribution of external forces, creation of internal forces, and an additional loop adding the elastic displacements due to the applied forces to the planned robot positions. The feedback level is organized in the form of an active compliance control law. For adjusting the controller to the, in general, unknown flexible behaviour, which in practice is the main problem of the controller design, a quasi-static model of the system is derived for different contact cases of the object and a procedure is presented, which by use of this model is capable of determining the compliance of the considered system and therefore of adjusting the controller. Experiments with two puma-type robots have been conducted to show the applicability of the self-adjusting control strategy. The task has been to grasp and move an unconstrained object. It is shown, that the system can adjust the control parameters to the unknown system compliance and that the control performance is improved considerably.     

A learning algorithm for improved hybrid force control of robotarms

An investigation on the hybrid force control of robot arms by learning is presented. A well-known force control scheme based on feedback linearization is used to build up an algorithm which improves, trial by trial, force and position tracking over a finite time interval. Differently from other published learning control schemes, the proposed algorithm does not rely on high gain feedback. Robustness and convergence in spite of sufficiently small system parameter uncertainties and disturbances is proven by means of the contraction mapping principle     

Synthesis of minimum-time control functions with multiple constraints by functional analysis!

This paper presents the functional analysis and iterative procedure for the minimum-time control problem subject to energy and magnitude constraints on the control functions. The necessary change of Swiger's method is described to solve a multi-boundary problem and numerical results are presented for a linear control system.     

Variable structure control scheme for landing on a celestial object

This paper considers the landing of a space vehicle on a celestial object. By assuming the air drag in two specific forms and the uncertainty in matching type, their effects are studied. Through the construction of a time-varying boundary layer, a new guidance control law for landing on a celestial object is proposed via the variable structure control (VSC) technique to guarantee that tracking performance is achieved at an exponential convergence rate. The proposed guidance law is continuous and alleviates chattering drawback by classic VSC design. Finally, simulation results are presented to illustrate the use of the main design.     

Two strategies of position and force control for two industrial robots handling a single object

The simultaneous position and force control problem for two industrial robots in handling a single object is studied in this paper. Two strategies, position-position control and position-force control, are first proposed. Stability analysis is then conducted for the strategies. Both strategies result in a stable system for simple robotic models. Steady state error is also studied for the strategies. Finally, experimental results are presented to evaluate the two strategies.     

On the linear quadratic minimum-time problem

A nontraditional minimum-time problem that includes quadratic-state and control-weighting terms in the performance index is investigated. This formulation provides a convenient solution to the problem that uses the solution of the Riccati equation to compute the optimal feedback gain and the optimal time. In some cases the latter is simply found using the derivative of the Riccati equation solution     

Adaptive control of multiple mobile manipulators transporting a rigid object

International Journal of Control, Automation and Systems - This paper presents a nonlinear control scheme for multiple mobile manipulator robots (MMR) moving a rigid object in coordination. The...     

On a motion control problem for an object in a conflict environment

The evasion problem of a mobile object from detection by a stationary observer in a passive mode is solved. For the case of power dependence of the level of the radiated signal on the motion velocity, a control law for velocity and the trajectory of the object that provide a minimum to the integral level of the signal coming to the observer input for the time of object motion are found in an explicit form.     

Solving function distribution and behavior design problem for cooperative object handling by multiple mobile robots

This paper addresses the function distribution and behavior design problem for a multirobot system which incorporates a behavior-based dynamic cooperation strategy for object handling. The proposed multiple robot system is composed of a managing robot and homogeneous behavior-based robots. The cooperation strategy in this system is realized in two steps: designing the distributed robot's cooperative behavioral attributes according to the robot's abilities, and organizing these behavioral attributes so that team cooperation is realized. For indicating an incremental style of local behavior construction, an advanced design of cooperative behavior for coping with unknown disturbance is addressed. Additionally, two extended cooperation strategies designed for a path tracking task are described. These three strategies are based on the same concept on performing manipulation in coordination. Therefore, by considering the function distribution among the managing robot and worker robots, and considering behavior design of each worker robot, the proposed system is able to achieve the object handling task with different performances according to the task requirement, such as with or without path tracking and with or without contact with the environment. Experimental results demonstrate the applicability of the proposed system.     

Approximation law for discrete-time variable structure control systems

Two approximation laws of sliding mode for discrete-time variable structure control systems are proposed to overcome the limitations of the exponential approximation law and the variable rate approximation law. By applying the proposed approximation laws of sliding mode to discrete-time variable structure control systems, the stability of origin can be guaranteed, and the chattering along the switching surface caused by discrete-time variable structure control can be restrained effectively. In designing of approximation laws, the problem that the system control input is restricted is also considered, which is very important in practical systems. Finally a simulation example shows the effectiveness of the two approximation laws proposed.     

Approximation law for discrete-time variable structure control systems

Two approximation laws of sliding mode for discrete-time variable structure control systems are proposed to overcome the limitations of the exponential approximation law and the variable rate approximation law. By applying the proposed approximation laws of sliding mode to discrete-time variable structure control systems, the stability of origin can be guaranteed, and the chattering along the switching surface caused by discrete-time variable structure control can be restrained effectively. In designing of approximation laws, the problem that the system control input is restricted is also considered, which is very important in practical systems. Finally a simulation example shows the effectiveness of the two approximation laws proposed.     

面向空间目标交汇的多拦截器最优部署算法

对空间目标的交汇拦截是现代空天防御体系部署的关键环节, 而其核心优化控制问题为实现交汇次数的最大化. 本文针对一类多个拦截器与空间目标交汇的最优问题, 提出了同时优化拦截器初始部署位置和机动过程中加速度的最优控制策略. 首先, 建立了同时考虑了部署地域和动力学约束的交汇次数最大化的最优控制模型. 进一步, 给出了拦截器与目标可交汇的必要条件以及最优加速度输入设计, 进而使得将最优控制问题转为拦截器部署位置的优化问题. 最后, 严格给出了各个拦截器最优部署位置的具体计算过程.     

On the robust control of two manipulators holding a rigid object

In this paper, a control architecture is developed for the closed chain motion of two six-joint manipulators holding a rigid object in a three-dimensional workspace. Dynamic and kinematic constraints are combined with the equations of motion of the manipulators to obtain a dynamical model of the entire system in the joint space. Reduced-order dynamic equations are then developed with regard to the position and force control variables. Robust control laws are then determined such that the force and position control design is decoupled. The control laws that will be discussed are: a robust position tracking controller that yields an exponentially stable position tracking error result, and a robust force tracking controller that yields adjustable bounds on the force tracking error.     

Vision-based integrated system for object inspection and handling

Image-based effector servoing is a process of perception–action cycles for handling a robot effector under continual visual feedback. This paper applies visual servoing mechanisms not only for handling objects, but also for camera calibration and object inspection. A 6-DOF manipulator and a stereo camera head are mounted on separate platforms and are steered independently. In a first phase (calibration phase), camera features are determined like the optical axes and the fields of sharp view. In the second phase (inspection phase), the robot hand carries an object into the field of view of one camera, then approaches the object along the optical axis to the camera, rotates the object for reaching an optimal view, and finally the object shape is inspected in detail. In the third phase (assembly phase), the system localizes a board containing holes of different shapes, determines the hole which fits most appropriate to the object shape, then approaches and arranges the object appropriately. The final object insertion is based on haptic sensors, but is not treated in the paper. At present, the robot system has the competence to handle cylindrical and cuboid pegs. For handling other object categories the system can be extended with more sophisticated strategies of the inspection and/or assembly phase.     

Development of the remote-controlled platform truck for handling heavy object and the remote control human interface for the disaster response

General interest for robotic technology has been increased by the public and the media after Fukushima Daiichi Nuclear Power Plant (hereafter referred to as 1F) disaster. Especially, robots which can work under the very severe condition where personnel cannot access have demands for development. As to respond to such high demands, NEDO established ‘Disaster response unmanned systems development project’ in 2012.[1] This project is specialized in the development of various remote-controlled equipment, such as remote-controlled platform truck and remote control human interface under ‘Mobile Robot Development’. Remote-controlled platform truck is designed to safely and surely deliver robots and supplies, instead of using stairs and elevator, etc. in and out of building where it is too critical for personnel to work under. Remote control human interface for robots is designed to standardize the command and operation screen for operator, based on opinions from project members, and manned facility construction.[2] In this article, mechanical structure and development tasks for remote-controlled platform truck, and commonalization approach for operation and camera display of various remote-controlled equipment and robot for remote control human interface are stated. Background: due to hydrogen explosion triggered by The Great East Japan Earthquake on 11 March 2011, a reactor building at Fukushima Daiichi Nuclear Power Plant was severely damaged. It is required to reduce high radiation dose in the atmosphere of the reactor building to perform restoration. To pursue decontamination of the reactor building, equipment to lift and carry decontamination devices to upper floor are required.     

Grasping the not-so-obvious: vision-based object handling for industrial applications

This article reports on several industrial applications of a visually guided system for robot grasping using an inexpensive two-finger gripper. In all cases, the robot uses visual information as input and is able to reason about the shapes of objects in a scene in order to decide the best stable grasp online. The first version of this system was able to grasp rectangular parts in arbitrary positions in the scene and was successfully deployed. New applications in industry have been addressed that must cope with the cost, time, and reliability requirements imposed by the industrial process. The results show that the capabilities of the underlying methodology make it feasible to deal with more complex shapes, even a priori unknown, opening up new possibilities within industrial domains, such as the food industry, that has traditionally not been fully automated due to a large variability in the shaper of the objects to be handled.