Development and hybrid force/position control of a compliant rescue manipulator

Performing search and rescue tasks in the ruins after disasters demand rescue robots with slender and compliant structure to accommodate the complicated configurations under debris. This paper presents the structural design and system composition of a novel tendon-sheath actuated compliant rescue manipulator with slender and flexible body. The proposed robot can drill into the narrow space where rescuers and traditional rigid robots cannot get in because of size limitation or toxic environment. The self-sensing calibration, dynamic modeling, and hybrid force/position control trajectory of the compliant gripper with integrated position and force monitoring capabilities are analyzed and discussed. With the aim of regulating the gripper displacement and clamping force during operation, a hybrid force/position control strategy is proposed based on a cascaded proportional-integral-derivative (PID) controller and a fuzzy sliding mode controller (FSMC). Experimental setups mainly consisting of servo motor, tendon sheath transmission components, compliant gripper, and real-time control system are established to calibrate the strain gauge sensors and identify the dynamic model parameters. Further experimental investigations involving force tracking experiments, position tracking experiments, and object grasping experiments are carried out. The experimental results demonstrate the effectiveness of the developed self-sensing approach and control strategies during rescue operation.     

A unified approach to position and force control by fuzzy logic

This paper proposes a unified control strategy of position and force. The authors' technique is based on impedance control with fuzzy logic and realizes the smooth shift from position control to force control and vice versa. At first, a robust impedance controller based on a disturbance observer is shown, and the method to unify the position and the force control through one controller is described. Next, an algorithm to estimate the dynamic characteristics of the environment is shown, and a force tracking control using the estimated parameters is proposed. Finally, the unified control algorithm of position and force based on fuzzy logic is established. The validity of this method is confirmed by several experimental results     

Humanitarian mine detecting six-legged walking robot and hybrid neuro walking control with position/force control

Now as many as 90 million anti-personnel mines are left buried and continue to kill or injure many people all over the world. The Cold War has already ended. However, regional wars and conflicts continue to break out one after another and new mines are being buried. As a collaboration of the world’s top-level nations in robotics, the leading countries should promote surveys and research to detect and dispose of these anti-personnel mines for the ultimate good of the environment by using its advanced robotics technologies. Our project has developed and studied high instrumentation technologies for mine detection, then mine detection strategies using measuring equipment mounted on walking robots based on six-legged teleoperated high technology.     

An experimental study on improving hybrid position/force control of a robot using time delay control

Robot position/force control has been a difficult task owing to the interaction between a robot and the environment. In addition to the dynamic instability, the interaction causes the following problems: (1) the dynamic coupling effect of the robot; (2) positional disturbance due to the uncertain surface of the environment with which the robot is in contact; and (3) vibration at steady state. To solve these problems, time delay control (TDC), well known for its robustness to plant uncertainties and disturbances, has been used as a baseline control law for hybrid control. In conjunction with TDC, the following three ideas were also used. (i) To reduce the dynamic coupling, a more accurate mass matrix was used instead of the constant mass matrix. (ii) To reject positional disturbance from the environment, force derivatives instead of position derivatives were used in the TDC law. (iii) Finally, to reduce the amplitude of the vibration at steady state, a novel scheme was adopted to enhance the resolution of A/D conversion for the force sensor. Experiments showed obvious improvements in the quality of the hybrid control, thereby clearly demonstrating the effectiveness of TDC with the proposed ideas.     

Technical Note Application of position/force control to scale calibration

In this paper, we present the application of position/force control strategy to the calibration phase automation of weighing systems. The objective is to test scales reliability all around the weighing surface with a precision of 100 g. To do this, we propose a structure composed of an electric jack able to exert a force on the scale. The controller aims to make the jack follow the desired force with a stabilization time inferior to 1 s. This system allows, on one hand, to highly decrease the testing phase and, on the other hand, to increase the scale reliability. The control strategy is based on the two main principles coming from force controllers, as developed in the literature: impedance control and hybrid position/force control. Experimental results are presented. Their study reveals a satisfactory system behavior ( fast response and good accuracy) with the switching control.     

Spatial hybrid/parallel force control of a hexapod machine tool using structure-integrated force sensors and a commercial numerical control

Structure-integrated force measurement in hexapod structures or kinematics offers great potential for spatial process force control in six degrees of freedom. Although force control has been studied for many years, research questions remain unanswered, especially when regarding parallel kinematic machine tools with numerical control and integrated sensors. This contribution summarizes the technology of structure-integrated force sensing in hexapod machine tools and develops two approaches to use the measured signals for direct hybrid/parallel force control. For different use-cases, such as teach-in or synchronous force/position control with variable task frame, different approaches of set-point specification and injection of manipulated values are studied from a practical point of view. As a result of the work, the feasibility of the force control with structure-integrated sensors on a commercial CNC can be confirmed through appropriate experiments. Furthermore, the realized G-Code integration represents a practical solution for programming force-controlled machine tools in an easy and concise way from the NC programme.     

A hybrid Eulerian-Lagrangian approach for thickness, correspondence, and gridding of annular tissues.

We present a novel approach to efficiently compute thickness, correspondence, and gridding of tissues between two simply connected boundaries. The solution of Laplace's equation within the tissue region provides a harmonic function whose gradient flow determines the correspondence trajectories going from one boundary to the other. The proposed method uses and expands upon two recently introduced techniques in order to compute thickness and correspondences based on these trajectories. Pairs of partial differential equations are efficiently computed within an Eulerian framework and combined with a Lagrangian approach so that correspondences trajectories are partially constructed when necessary. Examples are presented in order to compare the performance of this method with those of the pure Lagrangian and pure Eulerian approaches. Results show that the proposed technique takes advantage of both the speed of the Eulerian approach and the accuracy of the Lagrangian approach.     

A series active power filter adopting hybrid control approach

The series active power filter (APF) is suitable for compensating a voltage type harmonics-producing load, whereas the control approach it adopts may directly influence its compensation characteristics. This paper first discusses the control approach of detecting source current in terms of the basic operation principle of a series APF, then developing a control approach of detecting load voltage. On the basis of these, a hybrid control approach is proposed. In this approach, the reference signal of the compensation voltage needed by the series APF is obtained by detecting both source current and load voltage. Thus, this approach has the advantages of the first and the second control approaches and, at the same time, it can overcome their respective drawbacks. For practical realization, the control methods of the PWM inverter in the series APF and for regulating its DC side voltage are discussed in detail. A prototype of the series APF is manufactured and corresponding experimental investigation is done. The results show that when the series APF, if adopting the hybrid control approach instead of the other two, compensates for the voltage type harmonics-producing load, its performance can be improved greatly     

Use of hybrid models for testing and debugging control software for electromechanical systems

This paper proposes a hybrid modeling language and its application to a simulator-based testing and debugging environment for the control software for electromechanical systems. The new hybrid modeling language is designed mainly focusing on simulation speed, flexibility in connecting with control software, and model reusability. This language maintains the advantages of existing hybrid modeling languages such as Hybrid cc, including the flexibility of constraint programming and the reusability of the object-oriented approach. A new feature of the language is that it allows combination of compositional constraint programming and sequential procedural programming. The compiled code is executed efficiently by the runtime system, which has a built-in mechanism for communicating with external software, eliminating the complicated setup required for integrating the simulator with the control software. Model components programmed by the object-oriented approach allow designers to use existing components and to concentrate on the task of modeling the newly designed hardware. The runtime system has been integrated with a three-dimensional kinematics simulator and a control software design tool to create a simulator-based testing and debugging environment. The effectiveness of this system has been confirmed through its application to real product design projects.     

A hybrid Yee algorithm/scalar-wave equation approach

In this paper, two alternate formulations of the Yee algorithm, namely, the finite-difference time-domain (FDTD) vector-wave algorithm and the FDTD scalar-wave algorithm are examined and compared to determine their relative merits and computational efficiency. By using the central-difference divergence relation the conventional Yee algorithm is rewritten as a hybrid Yee/FDTD scalar-wave algorithm. It is found that this can reduce the computation time for many 3-D open geometries, in particular planar structures, by approximately two times as well as reduce the computer-memory requirements by approximately one-third. Moreover, it is demonstrated both mathematically and verified by numerical simulation of a coplanar strip transmission line that this hybrid algorithm is entirely equivalent to the Yee algorithm. In addition, an alternate but mathematically equivalent reformulation of the Enquist-Majda absorbing boundary condition based on the normal field component (relative to the absorbing boundary wall) is given to increase the efficiency of the hybrid algorithm in the modeling of open region problems. Numerical results generated by the hybrid Yee/scalar-wave algorithm for the Vivaldi antenna are given and compared with published experimental work     

A two-stage hybrid approach for CCI/ISI reduction with space-timeprocessing

We present a hybrid approach for separate cochannel interference (CCI) reduction and intersymbol interference (ISI) equalization in a slow Rayleigh fading channel. In this hybrid approach, a space-time filter is designed to maximize signal-to-interference-plus-noise ratio (SINR) by jointly optimizing the weight vector and the modified channel vector. A Viterbi equalizer then follows to equalize ISI and demodulate data symbols without noise enhancement. We derive an eigenvector solution for the joint optimization of the weight vector and the modified channel vector. Simulation results show good performance even at low carrier-to-interference-ratio (CIR)     

A hybrid backtracking search algorithm with wavelet mutation-based nonlinear system identification of Hammerstein models

In this paper a novel and accurate approach is presented to identify varieties of nonlinear Hammerstein models (closed loop and open loop) with the help of an optimization algorithm that combines a recently proposed backtracking search algorithm with wavelet theory-based mutation scheme (BSA-WM). The optimum output MSE associated with each plant along with its statistical information justifies the better precision and accuracy of BSA-WM-based identification approach as compared to the other methods reported in earlier literature.     

Intelligent position/force controller for industrial robotmanipulators-application of fuzzy neural networks

An intelligent controller, which consists of an intelligent planner and an adaptive fuzzy neural position/force controller, is proposed for a robot manipulator. The proposed controller deals with the human expert knowledge and skills for planning and control. In this paper, it is applied to the task of deburring with an unknown object. The effectiveness of the proposed controller is evaluated by computer simulations     

A ray-tracing/PMM hybrid approach for determining wave propagationthrough periodic structures

An approach to apply the ray-tracing method and the periodic moment method (PMM) for determining wave propagation through periodic material structures is presented. The PMM can be used to obtain the reflection and transmission properties of the periodic objects for plane-wave incidence. Those PMM solutions may then be employed in the ray-tracing method to simulate wave propagation, which includes scattering due to periodically distributed bodies. In the ray-tracing/PMM hybrid approach, results of specular reflections/transmissions and grating-lobe scattering at certain angles of incidence over both faces of the periodic structures are first evaluated. Then, those data are used in the ray-tracing program to calculate the effects of waves incident upon sections of periodic material structures. When a ray tube (composed of four rays) illuminates the periodic objects, some reflected and transmitted ray tubes are generated by interpolating the PMM data for each ray. Those ray tubes are then further traced to find their contributions at the location of the receiving antenna. Measurements of waves propagating in a staircase at 900 and 1800 MHz have been performed and compared with the ray-tracing/PMM simulations. Each section of the stairs is modeled as a singly periodic wedge panel having material properties similar to those of the reinforced concrete wall. Good agreements have been obtained     

Fuzzy adaptive force control of industrial robot manipulators with position servos

A fuzzy adaptive force control algorithm is suggested for commercialized industrial robots equipped with position servo drives in cascade with a software filter for the control of acceleration/deceleration profile to avoid vibrational shocks due to a sudden start or stop, where the control algorithm is composed of a Fuzzy Interpolation Logic Controller (FILC) and a Fuzzy Adaptive Stiffness Estimator (FASE FILC determines a control action according to the magnitude of an environmental stiffness in such a way that good force response is maintained regardless of changes of environmental stiffness. Specifically, some fuzzy controllers are designed for several representative environmental stiffness values, and then a control action for an estimated environmental stiffness value which is not the same as any representative stiffness values is decided by fuzzily aggregating different control actions of those fuzzy controllers. Here, FASE plays the role of estimating an environmental stiffness value and transfers the estimated stiffness value to FILC. To show the validity of the proposed adaptive fuzzy force controller, several numerical examples and some experimental results are illustrated, where soft, medium and hard environments are considered.     

Nonparametric identification of population models: an MCMC approach

The paper deals with the nonparametric identification of population models, that is models that explain jointly the behavior of different subjects drawn from a population, e.g., responses of different patients to a drug. The average response of the population and the individual responses are modeled as continuous-time Gaussian processes with unknown hyperparameters. Within a Bayesian paradigm, the posterior expectation and variance of both the average and individual curves are computed by means of a Markov Chain Monte Carlo scheme. The model and the estimation procedure are tested on both simulated and experimental pharmacokinetic data.     

A hierarchical defect repair approach for hybrid nano/CMOS memory reliability enhancement

Due to the small size of nanoscale devices, they are highly prone to process disturbances which results in manufacturing defects. Some of the defects are randomly distributed throughout the nanodevice layer. Other disturbances tend to be local and lead to cluster defects caused by factors such as layer misalignments, line width variations and contamination particles. In this paper, initially a method is proposed for separately identifying cluster defects from random ones. Subsequently a hardware repair structure is presented to repair the cluster defects with rectangular window transfer vectors using a range-matching content addressable memory (RM-CAM) and random defects using defect aware triple-modular redundancy (DA-TMR) columns. It is shown that a combination of these two approaches is more effective for repairing defects at higher error rates with an acceptable overhead. The effectiveness of the technique is shown by examining defect recovery results for different fault distribution scenarios. Also the mapping circuit hardware performance parameters are presented for various memory sizes and the speed, power dissipation and overhead factors are reported.     

基于一般散射模型的Hybrid Freeman/Eigenvalue分解算法

提出了一种新的基于一般散射模型的hybrid Freeman/eigenvalue分解算法,用于分析极化合成孔径雷达(PolSAR)数据.文中,单位矩阵作为体散射模型,相干矩阵的两个较大特征值对应的特征向量作为表面散射模型和二次散射模型,并且不需要反射对称条件.新算法有三个优点:第一,表面散射和二次散射不需要反射对称条件,更符合一般散射体的建模;第二,因为散射能量是相干矩阵特征值的线性组合,所以散射能量具有旋转不变性;第三,表面散射能量和二次散射能量避免了负值现象.在San Francisco地区的AIRSAR数据上进行了实验,证明了新算法的有效性.     

A parametric optimization approach to admission control and bandwidth assignment in hybrid TDM networks

The access to a multiservice synchronous TDM network is considered, where hybrid frames are used to carry two basic traffic types (a circuit-switched isochronous and a packet-switched asynchronous one), generated by several users. Each user is assigned a portion of the total available bandwidth, in terms of slots/frame, which is dynamically allocated between the two traffic types at the user premises, by means of a local randomized decision rule. The users' bandwidth shares (capacities) are allocated by a centralized agent, whose goal is to minimize a global cost function that accounts for packet delays and call blocking of the entire process. Parametric optimization problems for the central agent are defined and the application of suitable descent techniques is shown, with the cost function extending over a finite and an infinite time horizon, respectively. The specific nature of the optimization problems is discussed, and numerical examples and simulations are presented that illustrate the effectiveness of the method.     

Parameter identification and position control for helical hydraulic rotary actuators based on particle swarm optimization

It is difficult to obtain an accurate mathematical model in electro-hydraulic servo control system, due to the nonlinear factors such as dead zone, saturation, flow coefficient, and friction. Hence, a parameter identification algorithm, combining recursive least squares (RLS) with modified nonlinear particle swarm optimization (NPSO) algorithm, is proposed. On this basis, another improved NPSO algorithm is also put forward, aiming at searching for the optimal proportional–integral (PI) controller gain of the nonlinear hydraulic system while giving comprehensive consideration to the system performance indexes. The system identification experiments and position tracking control are conducted, respectively. As indicated by the comparison with the least squares (LS), RLS, PSO, and RLS–LPSO results, the proposed method shows higher identification and control accuracy.