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OF the 450 plus numerical control systems for machine tools currently being used in the United Kingdom, well over 100 systems are being operated by companies in or associated with the aircraft industry. In fact, the aircraft industry has probably done more than any other industry to pioneer, encourage and develop the use of numerically‐controlled machine tools. On the other hand, the application of numerical control within the aircraft industry itself is still in its infancy and it is therefore the purpose of this survey to outline the characteristics of the range of control systems now available. According to Report No. 119 entitled ‘Numerical Control: An Economic Survey’ by the Production Engineering Research Association of Great Britain, a survey revealed that many of the early applications of numerical control to machine tools were carried out without being economically justified. At that time, many of the advantages of numerical control were highlighted while some of the problems associated with their use were either not fully understood or ignored. However, the experience gained by a number of operators over a period of years has now put the use of this type of equipment into proper perspective. Since numerically‐controlled machine tools cost between li to 4 times as much as conventional machines it is necessary to justify this higher cost by direct or indirect savings. The direct savings, which can be measured and expressed in terms of time and money or both, may occur in (i) the pre‐production stage, by the simplification or elimination of jigs and tools, (ii) the production stage, by the elimination of marking‐out and reductions in setting, machining, handling and inspection times, and (iii) the assembly stage, by reductions in fitting or assembly times as a result of improved product quality. Indirect savings, which tend to be intangible, are: the reduction in lead times, the ease of design modification, the savings in scrap or rectification work, the reduction in jig and tool storage costs, and the reduction of operator fatigue. However, the picture has its greyer tones, and to brighten these a joint study convention was recently held by the British Electrical and Allied Manufacturers' Association and The Machine Tool Trades Association to foster such improvements as: the adoption of a common programming approach involving if possible a common numerical control language, the development of new machine tools specifically intended for use with numerical control systems and a greater degree of Government support for the introduction of numerically‐controlled machine tools used on Government production contracts. It is not the purpose of this article to describe the performance of machine tools equipped with numerical control systems but merely to present a survey of systems available. However, wherever possible examples have been quoted of the application of the numerical control system to particular machine tools—and a large number of these to machine tools being used in the aircraft industry. For a more detailed account of the application of numerically controlled machine tools, the reader is referred to the article beginning on p. 232, and to PERA Report No. 119. This PERA Report is a major contribution to literature on this subject and we are happy to acknowledge the use of a certain amount of the information contained in that Report in the following article.

Component positioning is an important part of aircraft assembly, aiming at the problem that it is difficult to accurately fall into the corresponding ball socket for the ball head connected with aircraft component. This study aims to propose a ball head adaptive positioning method based on impedance control.

First, a target impedance model for ball head positioning is constructed, and a reference positioning trajectory is generated online based on the contact force between the ball head and the ball socket. Second, the target impedance parameters were optimized based on the artificial fish swarm algorithm. Third, to improve the robustness of the impedance controller in unknown environments, a controller is designed based on model reference adaptive control (MRAC) theory and an adaptive impedance control model is built in the Simulink environment. Finally, a series of ball head positioning experiments are carried out.

During the positioning of the ball head, the contact force between the ball head and the ball socket is maintained at a low level. After the positioning, the horizontal contact force between the ball head and the socket is less than 2 N. When the position of the contact environment has the same change during ball head positioning, the contact force between the ball head and the ball socket under standard impedance control will increase to 44 N, while the contact force of the ball head and the ball socket under adaptive impedance control will only increase to 19 N.

In this paper, impedance control is used to decouple the force-position relationship of the ball head during positioning, which makes the entire process of ball head positioning complete under low stress conditions. At the same time, by constructing an adaptive impedance controller based on MRAC, the robustness of the positioning system under changes in the contact environment position is greatly improved.

The position/force control of the robot needs the parameters of the impedance model and generates the desired position from the contact force in the environment. When the environment is unknown, learning algorithms are needed to estimate both the desired force and the parameters of the impedance model.

In this paper, the authors use reinforcement learning to learn only the desired force, then they use proportional-integral-derivative admittance control to generate the desired position. The results of the experiment are presented to verify their approach.

The position error is minimized without knowing the environment or the impedance parameters. Another advantage of this simplified position/force control is that the transformation of the Cartesian space to the joint space by inverse kinematics is avoided by the feedback control mechanism. The stability of the closed-loop system is proven.

The position error is minimized without knowing the environment or the impedance parameters. The stability of the closed-loop system is proven.

The gait planning and control of quadruped crawling robot affect the stability of the robot walking on a slope. The control includes the position control in the swing phase, the force control in the support phase and the switching control in the force/position switching. To improve the passing ability of quadruped crawling robot on a slope, this paper aims to propose a soft control strategy.

The strategy adopts the statically stable crawling gait as the main gait. As the robot moves forward, the position/force section switching control is adopted. When the foot does not touch the ground, the joint position control based on the variable speed PID is performed. When the foot touches the ground, the position-based impedance control is performed, and a fuzzy multi-model switching control based on friction compensation is proposed to achieve smooth switching of force and position.

The proposed method offers a solution for stable passage in slope environment. The quadruped crawling robot can realize smooth switching of force/position, precise positioning in the swing process and soft control of force in the supporting phase. This fact is verified by simulation and test.

The method presented in this paper takes advantage of minimal tracking errors and minimal jitters. Simulations and tests were performed to evaluate the performance.

The purpose of this paper is to propose a hybrid position/force control scheme using force and vision for docking task of a six degrees of freedom (6-dof) hydraulic parallel manipulator (HPM).

The vision system consisted of a charge-coupled device (CCD) camera, and a laser distance sensor is used to provide globe relative position information. Also, a force plate is used to measure local contact forces. The proposed controller has an inner/outer loop structure. The inner loop takes charge of tracking command pose signals from outer loop as accurate as possible, while the outer loop generates the desired tracking trajectory according to force and vision feedback information to guarantee compliant docking. Several experiments have been performed to validate the performance of the proposed control scheme.

Experiment results show that the system has good performance of relative position tracking and compliant contact. In whole docking dynamic experiment, the amplitudes of contact forces are well controlled within 300 N, which can meet perfectly the requirement of the amplitude being not more than 1,000 N.

A hybrid position/force control scheme using force and vision is proposed to make a 6-dof HPM dock with a moving target object compliantly.

Flexible tooling for adjusting the posture of large components of aircraft (LCA) is composed of several numerical control locators (NCLs). Because of the manufacture and installation errors of NCL, the traditional control method of NCL may cause great interaction force between NCLs and form the internal force of LCA during the process of posture adjustment. Aiming at this problem, the purpose of this paper is to propose a control method for posture adjustment system based on hybrid force-position control (HFPC) to reduce the internal force of posture adjustment.

First of all, the causes of internal force of posture adjustment were analyzed by using homogeneous transformation matrix and inverse kinematics. Then, axles of NCLs were divided into position control axle and force control axle based on the screw theory, and the dynamic characteristics of each axle were simulated by MATLAB. Finally, a simulated posture adjustment system was built in the laboratory to carry out HFPC experiment and was compared with the other two traditional control methods for posture adjustment.

The experiment results show that HFPC method for redundant actuated parallel mechanism (RAPM) can significantly reduce the interaction force between NCLs.

In this paper, HFPC is applied to the control of the posture adjustment system, which reduces the internal force of LCA and improves the assembly quality of aircraft parts.

In aircraft wing–fuselage assembly, the distributed multi-point support layout of positioners causes fuselage to deform under gravity load, leading to assembly difficulty and assembly stress. This paper aims to propose a hybrid force position control method to balance aerodynamic shape accuracy and deformation of assembly area, thereby correcting assembly deformation and reducing assembly stress.

Force and position control axes of positioners are selected based on screw theory and ellipsoid method. The position-control axes follow the posture trajectory to align the fuselage posture. To exert force on the fuselage and correct the deformations, the force-control axes follow the contact force derived by using orthogonal experiments and partial least squares regression (PLSR). Finite element simulation and one-dimension deformation correction experiment are conducted to verify the validity of this method.

Simulation results indicate that hybrid force position control method can correct assembly deformation and improve the wing–fuselage assembly quality significantly. Experiment on specimen verifies the effect of this method indirectly.

The proposed method gives a solution to solve the deformation problem during aircraft wing-fuselage assembly, thereby reducing assembly stress and improving assembly quality.

Intelligent pneumatic actuator (IPA) is a new generation of actuator developed for Research and Development (R&D) purposes in the academic and industrial fields. The purpose of this paper is to show the application of optical encoder and pressure sensor in IPA, to develop a real-time model similar to the existing devices, and to assess the position control performance using a proportional-integrative (PI) controller and a bang-bang controller in real-time.

A micro optical encoder chip is used to detect cylinder rod position by reading constructed laser stripes on a guide rod, whereas a pressure sensor is used to detect the chamber pressure reading. To control the cylinder movements by manipulating pulse-width modulation (PWM) cycles, two unit valves of two ports and two positions were used. A PI controller and a bang-bang controller are used with suitable gain value to drive the valve using PWM to achieve the target actuator position.

The results show the experimental results of the closed-loop position tracking performance of the system using a data acquisition (DAQ) card over MATLAB software.

This paper presents a real-time model used to replace the microcontroller-based system from previous IPA design. The paper proposes two control strategies, PI and bang-bang, to control position using encoder and pressure reading.

This paper seeks to present an acceleration‐based force‐impedance controller, applied to a six‐dof parallel mini‐manipulator: the robotic controlled impedance device (RCID).

The proposed control strategy involves three cascade controllers: an inner acceleration controller, built as a set of six single input/single output acceleration controllers (one per manipulator axis), an impedance task‐space controller, and an outer force controller.

The control strategy enables two kinds of manipulator behaviour: force‐limited impedance control and position‐limited force control. The type of behaviour depends only on the chosen manipulator trajectories.

The RCID may be used as a force‐impedance controlled auxiliary device, coupled in series with a position‐controlled commercial industrial robot. The two manipulators combined behave as a single manipulator, having the impedance and force control performance of the RCID, as well as the workspace and trajectory tracking performance of the industrial manipulator. The industrial manipulator should perform free space motion trajectory tracking, the RCID being kept in a “home” position, preserving its small workspace for impedance and force control.

A robust control strategy that enables good performance, while the robot executes tasks that involve interaction with the environment, is being proposed. Experimental results on a force‐impedance controlled six‐dof parallel mini‐manipulator are presented.

The purpose of this paper is to present a novel and accurate coordination control method of dual‐arm modular robot based on position feedback using 3D motion measurement system – Optotrak3020. The end‐position accuracy of dual‐arm modular robot can be improved obviously.

By means of Optotrak3020, the actual end‐position of dual‐arm modular robot is acquired and then returned to the robotic controllers, so the corresponding position error compensation is implemented. Through a 3D simulation and experiment of dual‐arm modular robot for tracking a trajectory of plane right triangle, the feasibility and validity of this control strategy are verified.

The coordination control of dual‐arm modular robot based on position feedback can be accomplished by means of Optotrak3020. The dual‐arm modular robot can accurately accomplish the task of positioning or tracking a reference trajectory.

This real‐time position feedback control method with high control accuracy can be implemented on a PowerCube dual‐arm modular robot system. This method also can be applied to other dual‐arm robot systems, such as mobile robot with dual‐arm, humanoid robot.

The coordination control method of dual‐arm modular robot is presented based on end‐position feedback using Optotrak3020 motion measurement system. The platforms of simulation, communication and experiment are developed, respectively.