Achievement of high scaling gain macro-micro bilateral control system

Precise force control and position control is essential for many robotic applications. During unilateral or bilateral object handling remote applications, human operators apply excess forces on the actuators with the intention of better grip and it is possible to damage the handled objects. This paper proposes position control and force control techniques when human applies excess force. The controllers consist of predefined force and equilibrium position which are correspond to remote environmental object safety. The operator applied excess force is modeled as a spring force through a virtual stiffness model. The paper introduces proportional derivative position control loop to conventional virtual stiffness controller. The force control loop and the position control loop references are combined in the common dimension of acceleration to produce current reference to the actuator. The sensorless sensing techniques of disturbance observer and reaction force observer are utilized to disturbance suppression and external force estimation. In the force controller, estimated reaction force is reduced to desired value by introducing virtual force loop between reaction force observer output and reaction force feedback input. The position control is achieved by introducing a scaling factor to reaction force feedback path. The switching between force control and position control is possible with scaling factor value. The performances of proposed methods are compared with conventional method and validity of the proposed methods is verified by simulations and experiments.

The learning control is applied to hybrid force and position control of robot manipulators. When the geometry and position of a constraint surface is known, the hybrid force and position controller and the feedforward compensator can be designed in the constraint coordinates. When the operation is periodic, the learning hybrid force and position control enhance the control performance as the feedforward compensator is updated in each cycle by the force and position error in the preceding trials. This scheme is proved to be asymptotically stable. A two degree of freedom SCARA-type direct-drive robot manipulator is used to test the learning hybrid force and position control. The deburring tool mounted on the upper link of the robot could follow a flat, tilted flat, and curved 1/4 " aluminum plate with a desired contact force of 10 N (within the root-mean-square force error of 1.95 N) and with a desired tangential velocity. The experiments confirmed the effectiveness of the learning hybrid force and position controller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In this paper, model-based precision force and position control of an ionic polymer metal composite (IPMC) is presented. A 23.8 mm × 3.4 mm × 0.16 mm IPMC strip was used as an actuator in a cantilever configuration. Open-loop force and position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeat-ability and reliability. After feedback controllers were designed and implemented with empirically obtained fourth-order plant transfer functions, the overshoot decreased from 460 to 2.8 per cent and the settling time was reduced from 37.5 to 3.22 s in force control. In position control the overshoot decreased from 333 to 20.3 per cent and the settling time was reduced from 21.5 to 2.56 s. Microscale precision force and position control capabilities of the IPMC actuator were also demonstrated experimentally. An 8 μN force resolution was achieved with a force noise of 0.5μN r.m.s., and the position resolution was 6 μm with a position noise of 2.5 μm r.m.s. The maximum force and tip displacement achieved with the IPMC actuator under closed-loop control were 2 mN and 5 mm respectively. The IPMC actuator could follow various commanded force and position trajectories such as sinusoidal and trapezoidal position profiles, and a velocity profile with a 3 mm/s maximum velocity. A novel hybrid force and position control strategy demonstrated its utility in practical micromanipulalion applications where the actuator force must be limited to prevent damaging micro-objects. High-precision control of the IPMC at low force level proved its potential for micromanufacturing and micromanipulation applications such as robotic and biomedical microgrippers.

The best exoskeleton control strategy depends on the task, motivating the development and analysis of an exoskeleton capable of position, force, and impedance control. In this paper, we implement and compare the three controller types via sliding mode control on a custom-built pneumatic cylinder ankle exoskeleton. To evaluate each controller's performance, the exoskeleton was tested on the benchtop and with human subject experiments. With the position controller, the exoskeleton achieved an root-mean-square error (RMSE) of under 5 deg for both the benchtop and human tests. It had a bandwidth of approximately 12 rad/s. The force controller tracked sinusoidal trajectories acceptably well at low frequencies (15% of force range at 6 rad/s), with a bandwidth of approximately 24 rad/s. The error was significantly higher (RMSE of 24% of force range) for the more biologically relevant trajectory. The impedance controller demonstrated the desired spring-like behavior, with position RMSE generally under 5 deg compared to expected position. All three controllers worked equally well for benchtop and human tests. Thus, a pneumatically powered ankle exoskeleton with sliding mode control is capable of accurate position and impedance control and is capable of marginally acceptable force control.

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

Two different control schemes, position model referenced control (PMRC) and force model referenced control (FMRC), are developed for a simplified two robots model with one interacting axis. The dynamic stability of the position (or force) control under the FMRC (or PMRC) is analyzed. Results indicate that PMRC, although providing better dynamic performance of the position control, may degrade the dynamic performance of the force control. However, FMRC can provide better dynamic performance of both position and force control.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This article presents a comparative study between the hybrid impedance control approach and the impedance force control approach with neural networks compensation of manipulator modeling errors. The proposed algorithm consists of an outer hybrid impedance control loop that generates the reference (target) acceleration to an inner inverse dynamics control loop. In order to improve the controller robustness, a compensation action of the manipulator modeling errors is introduced, acting on the target acceleration. This compensation action is based on a neural network model achieved by minimizing the modeling errors along the manipulator trajectory. The neural network algorithm uses an error training signal to model errors, that is minimized along the trajectory. The performance of the hybrid impedance control system with neural network compensation, is compared with the impedance force controller with neural network compensation, and is illustrated by computer simulations with a two degree-of-freedom PUMA 560 robot, whose end-effector is forced to move along a frictionless surface located perpendicular to the horizontal plane. The results obtained reveal even better performance when the desired force profile is not constant along the trajectory. This situation is very important in fine motion tasks where the desired force must have a varying profile along the trajectory, namely at the beginning and the end of the task. The results have also shown accurate force tracking and position control, even when significant uncertainties in the robot dynamic model are assumed.

Constrained motion of a planar rigid-flexible manipulator is considered in this study. a dynamic model with zero tip deformation constraint of constrained rigid-flexible 608

In the recent assembly lines, the frequency of changing processes has been increasing in line with high mix production, but because these changes are carried out by operator, the burden of changing processes has increased as well. This situation has arisen because of the fact that since the robots being used at present automatic assembly lines are based on a simple teaching and playing back method, human workers must renew instructions for each act of changing a work object and also that dedicated machines are necessary due to the inability of making precision assembly,thereby inviting declines in total operational rates and increases in cost. These facts are limiting the use of robot based automation itself and are one of the important factors for the declining international competitive power. Under these circumstances, with the aim of constructing sophisticated production systems that are capable of dealing with process changes automatically without the use of human labor, a project called ""Research &amp; Development of Process Adaptive Flexible Robots""was proposed and was adopted to the Regional Consortium Research and Development Enterprise supported by the Ministry of Economy, Trade and Industry and by the New Energy and Industrial Technology Development Organization, and was adopted. The research period was to be 3 years from the fiscal year 1997 to the fiscal year 1999, and the total research fund was to be 360 million yen. In more specific terms, an engine assembly line and a semiconductor testing process were chosen as research subjects; and developmental research was carried out for elemental techniques that are necessary for the flexible execution of tasks such as piston insertion causing no damage to walls even with a minute clearance, or IC chip insertion causing no plastic deformation even with positional dislocation, though these tasks must be carried out when works change in type, size, etc.; and the researchers started the work of developing system integration technology that would achieve these task objectives in the optimal manner. Attention was focused rather on ""force control"" of which humans make skillful use than on developmental work based on the conventional position control technology, and development objectives were set not only to achieve a breakthrough for putting force control technology into practice by way of the integration of flexible force control and high aprecision position control and also by way of controlling the vibrations of complex machine systems, but also to demonstrate the research results by means of two prototypes of a flexible robot for assembly lines and an inserter for IC chip testing. The present special issue is a collection of results achieved by the participating research organization in the present research and development work, and it will be a great pleasure for its editors if this issue contribute seven a little. toward the future practical use of force control. Finally, sincere appreciation is expressed to the Ministry of Economy, Trade and Industry and the New Energy and Industrial Technology Development Organization for providing an opportunity for carrying out this research and development work, as well as to all the organizations for their participation in the project.

To address the demands for precision and load-bearing capacity in the installation of building panels, a hybrid force-position driven robot with redundant actuation has been developed. The mechanical performance of this robot is primarily governed by its central parallel mechanism, which is equipped with redundant actuators matching the degrees of freedom. Non-redundant and redundant actuators are respectively responsible for position and force control. The inclusion of redundant force-driven joints has increased the internal coupling within the mechanism. To enhance the coordination between position and force control, a hybrid synchronized control method based on cross-coupling has been proposed. Initially, kinematic and dynamic models of the parallel structure were established. Under predefined trajectories, the theoretical inputs for each actuator were calculated using inverse kinematics and dynamics. Subsequently, employing the principle of cross-coupling, the torque output from the position actuators was used as feedback. This feedback was processed by a synchronized coordination controller to adjust the output force of the redundant force-driven joints. By adjusting the output force of the redundant actuators, the torque burden on the position actuators was effectively reduced, thereby enhancing the precision of position control. Additionally, under the same load conditions, smaller power actuators could be utilized for position control, reducing the overall weight of the robot and improving its load-to-weight ratio. To validate the effectiveness of the proposed control strategy, a robotic simulation environment was established. The simulation results demonstrated significant reductions in the average torque required by the position actuators across three different trajectories, with reductions of 91.43%, 54.56%, and 80.6% respectively. Finally, the load-bearing capacity and the load-to-weight ratio of the prototype were assessed. Experimental results confirmed that the prototype achieved a load-to-weight ratio of 15.83%, validating the effectiveness of the hybrid synchronized control method based on cross-coupling.

There are many tasks which require robotic manipulators interaction with environment. It consists of three control problems, i.e., position control, impact control and force control. The position control means the way of reaching to the environment. The moment of touching to the environment yields the impact control problem and the force control is to maintain the desired force trajectory after the impact with the environment. These three control problems occur in sequence, so each control algorithm can be developed independently. Especially for redundant manipulators, each of these three control problems has been important independent research topic. For example, joint torque minimization and impulse minimization are typical techniques for such control problems. The three control problems are considered as a single task in this paper. The position control strategy is developed to improve the performance of the task, i.e., minimization of the individual joint torques and impulse. Therefore, initial conditions of the impact control problem are optimized at the previous position control algorithm. Such a control strategy yields improved result of the impact control. Similarly, the initial conditions for the force control problem are indirectly optimized by the previous position control and impact control strategies. The force control algorithm uses the individual joint torque minimization concept. It also minimizes the force disturbances. The simulation results show the proposed control strategy works well.

Automatic cell injection has been the focus of many researches and commercial development for several years. In this paper, a robotic cell injection system for automatic batch injection of suspended cells is developed. To facilitate the process, these suspended cells are held and fixed to a cell array by a specially designed cell holding device, and injected one by one through an “out-of-plane” cell injection process. A micropipette equipped with a PVDF micro force sensor is integrated in the proposed system. The force sensor is utilized to measure real time injection force applied to the cells during injection process. Through calibration of the relationship between the cell injection force and the desired injector pipette trajectory, a position (vision) and force control algorithm is proposed and applied to the motion control of the injection pipette in three-coordinate directions during an injection process. The out-of-plane cell injection task is decoupled into a position control in X-Y horizontal plane and an impedance force control in Z-axis. The depth motion of the injector pipette, a common problem of three-dimensional micromanipulation, is indirectly controlled by the force control. Finally, experimental results are given to demonstrate the effectiveness of the proposed approach.

This paper presents the performance validation of the motion control system for integration force and trajectory information. To realize the implementation high-quality motion that includes contact and non-contact motion to robot system, two contradictory systems; force and trajectory control should be synthesized in one control axis. In order to respond to the request, we proposed a motion synthesis system which integrates two controller in frequency domain. This paper firstly will discuss the acceleration control based force control and position control respectively. And it is also shown that the force reproducibility is decided by contact object's impedance. Then, performance analysis of the motion synthesis system will be shown. From the results, it is confirmed that the motion synthesis system satisfies two control goals without depending on impedance or presence of contact environment. The validity of the design approach is verified by experimental results.

Basen on researching into WDPSS-8, after analysing and comparing 3 support systems in wind tunnel including the strut suspension system, cable mounted system and wire-driven parallel suspension system, the following conclusions can be acquired. Till now the strut support systems and rotary balances can be used in measuring the dynamic derivatives of the aircraft in low-speed wind tunnels successfully, wire-driven parallel suspension system has a great potentiality, but it is still under investigation. The cable mounted system is one of suitable method for measuring the static derivatives of the aircraft in LSWT. Thoug it allows a large supporting stiffness, small interference of the streamline flow and a high measuring precision for large attack angle, it can not be used in measuring the dynamic derivatives. Wire-driven parallel suspension system has opened a new horizon for measuring the static and dynamic derivatives of the aircraft in LSWT. Using the same system based on positon control and force control in robotics, it allows to realize the free flight of the aircraft model and to obtain the static and dynamic derivatives. However, the results given in this Chapter can only be considered as a preliminary step in establishing feasibility although the wire-driven parallel suspension system is a very interesting design, and it may be sufficiently developed into a rountine practical system.

Time delay in bilateral control system seriously deteriorates stability. Conventional acceleration based bilateral control method has stabilized position control. But, force control is not stabilized. This paper proposed a stability improved structure for bilateral control system. Position control and force control of proposed bilateral control system are stabilized. The validity of the proposed method is shown by numerical and experimental results.