Sensorless point-to-point control for a musculoskeletal tendon-driven manipulator: analysis of a two-DOF planar system with six tendons

Tendon-driven robot utilizes only tensile force (i.e. tension) for motion generation. Therefore, a redundant actuation is characteristically necessary, and then it yields the internal force among tendons. Given the internal force for balance at a desired posture, the musculoskeletal tendon-driven manipulator has the inherent possibility of point-to-point position control without any sensory feedback. However, the motion convergence is strongly governed by the arrangement of tendons.This study analyzes the mathematical conditions of convergence for this sensorless position control by use of a Lyapunov function. Subsequently, targeting the two-link musculoskeletal structure with six tendons, the sufficient conditions for the convergence at desired posture are further defined by employing an approximation of the tendon-length based on a Taylor expansion. Finally, the convergent conditions are verified through simulation and validated via experimental results.     

基于硬件滤波电路的无刷直流电机转子位置辨识

反电动势过零检测是无刷直流电机无位置传感器控制中转子位置检测的主要方法之一,为消除PWM因素的影响,需要对转子位置检测电路进行滤波处理。本文采用硬件滤波器对反电动势过零检测电路进行滤波,既要考虑深度滤波带来的相移问题又要兼顾消除噪声的影响,分析滤波器的幅频特性和相频特性,根据反电动势过零检测指标要求设计滤波器参数,并用于无刷直流电机转子位置辨识和无位置传感器控制中。仿真结果和实验结果表明,所采用的滤波器及其参数能较好地检测出转子位置,可以明显提高无位置传感器无刷直流电机驱动系统的控制性能。     

线电感特征点定位的开关磁阻电机无位置传感器控制方法

针对目前开关磁阻电机(SRM)在无位置传感控制方面受磁路饱和影响而导致转子位置估算精度不高的问题,提出一种线电感特征点定位的开关磁阻电机无位置传感器控制方法.首先提出了线电感及其特征点的基本概念,分析了线电感与转子位置角度间的函数关系,研究了根据两相邻线电感特征点对应区间的位置角度及时间来确定电机转子在该区间的平均转速及下一对应区间位置估算的具体实现方法.最后通过仿真与实验验证了上述方法的可行性.     

Robust PD Control Using Adaptive Compensation for Completely Restrained Parallel-Wire Driven Robots: Translational Systems Using the Minimum Number of Wires Under Zero-Gravity Condition

A parallel-wire driven mechanism uses flexible wires instead of heavy rigid links. In this paper, we propose a robust point-to-point (PTP) position control method in the task-oriented coordinates for completely restrained parallel wire-driven robots, which are translational systems using the minimum number of wires under zero-gravity conditions. In the cases where parallel-wire driven robots are disassembled/assembled and used outdoors (also applied in space), actuator positions would be uncertain or contain some errors. The error of internal force among wires that results from such uncertainty of actuator positions deteriorates positioning performance. To overcome such a difficulty, adaptive compensation is employed for robust PD control against the error of internal force, in this paper. It is necessary for the adaptive compensation to separate the internal force term linearly into a regressor matrix and a parameter vector concerned with the errors of actuator positions. The internal force term, however, possesses the nonlinear characteristic concerned with the errors of actuator position. Noting the structure of the internal force term, this paper shows that measuring both the position of an end-effector and wire length in real time enables the linear separation. Not only does this robust PD control method ensure precise positioning using external sensors; it enhances the robustness for uncertainty of the Jacobian matrix, which results from the error of actuator installation. First, we explain the linearization of the internal force term. Next, the robust PD control for the parallel-wire driven system using the uncertain Jacobian matrix is proposed; then, we prove the motion convergence to desired points and discuss its robustness based on Lyapunov stability analysis. Finally, the usefulness of the proposed control method is demonstrated through experiments and simulations.     

Numerical analysis of feedforward position control for non-pulley musculoskeletal system: a case study of muscular arrangements of a two-link planar system with six muscles

In a musculoskeletal system like a tendon-driven robot, redundant actuation is necessary because muscles (or mechanical parts such as tendons) can transmit tension only unidirectionally. This redundancy yields internal force among muscles, which has a particular field of potential energy. Using internal force as a feedforward input, a musculoskeletal system can achieve feedforward position control with no sensory feedback. This paper studies the feedforward position control coming from the redundancy for a non-pulley musculoskeletal system. Targeting a planar two-link system with six muscles as a case study, the motion convergence depending on the muscular arrangement is examined quasi-statically. The results point out that the convergence is extremely sensitive to the muscular arrangement, and adding small offsets for the muscular connected points can remarkably improve the positioning performance.     

Algorithms for Sensorless Manipulation Using a Vibrating Surface

We describe a programmable apparatus that uses a vibrating surface for sensorless, nonprehensile manipulation, where parts are systematically positioned and oriented without sensor feedback or force closure. The idea is to generate and change the dynamic modes of a vibrating surface. Depending on the node shapes of the surface, the position and orientation of the parts can be predicted and constrained. The vibrating surface creates a two-dimensional force vector field. By chaining together sequences of force fields, the equilibrium states of a part in the field can be successively reduced to obtain a desired final state. We describe efficient polynomial-time algorithms that generate sequences of force fields for sensorless positioning and orienting of planar parts, and we show that these strategies are complete. Finally we consider parts feeders that can only implement a finite set of force fields. We show how to plan and execute strategies for these devices. We give numerical examples and experiments. and discuss tradeoffs between mechanical complexity and planning complexity. Received November 15, 1996; revised January 18, 1998.     

Adaptive hybrid force/position control of robot manipulators using an adaptive force estimator in the presence of parametric uncertainty

This study is devoted to sensorless adaptive force/position control of robot manipulators using a position-based adaptive force estimator (AFE) and a force-based adaptive environment compliance estimator. Unlike the other sensorless method in force control that uses disturbance observer and needs an accurate model of the manipulator, in this method, the unknown parameters of the robot can be estimated along with the force control. Even more, the environment compliance can be estimated simultaneously to achieve tracking force control. In fact, this study deals with three challenging problems: No force sensor is used, environment stiffness is unknown, and some parametric uncertainties exist in the robot model. A theorem offers control laws and updating laws for two control loops. In the inner loop, AFE estimates the exerted force, and then, the force control law in the outer loop modifies the desired trajectory of the manipulator for the adaptive tracking loop. Besides, an updating law updates the estimated compliance to provide an accurate tracking force control. Some experimental results of a PHANToM Premium robot are provided to validate the proposed scheme. In addition, some simulations are presented that verify the performance of the controller for different situations in interaction.     

Balancing of humanoid robot using contact force/moment control by task-oriented whole body control framework

Balancing control of humanoid robots is of great importance since it is a necessary functionality not only for maintaining a certain position without falling, but also for walking and running. For position controlled robots, the for-ce/torque sensors at each foot are utilized to measure the contact forces and moments, and these values are used to compute the joint angles to be commanded for balancing. The proposed approach in this paper is to maintain balance of torque-controlled robots by controlling contact force and moment using whole-body control framework with hierarchical structure. The control of contact force and moment is achieved by exploiting the full dynamics of the robot and the null-space motion in this control framework. This control approach enables compliant balancing behavior. In addition, in the case of double support phase, required contact force and moment are controlled using the redundancy in the contact force and moment space. These algorithms are implemented on a humanoid legged robot and the experimental results demonstrate the effectiveness of them.     

基于dsPIC30F6010的无传感器无刷直流电机控制

本文使用dsPIC30F6010来控制无传感器无刷直流(brushless DC,BLDC)电机,采用反电动势过零检测技术来确定转子的位置,两种可选的起动方法以适应特定负载,使用内部电流控制环来设置PWM占空比,速度控制环作为外部控制环。所实现的无传感器控制算法特别适用于风扇和泵。     

基于ST7的无传感器BLDCM控制系统设计

介绍了基于ST7FMC1K2单片机控制的无位置传感器无刷直流电机控制系统的设计。该系统通过反电动势法实现位置检测,同时给出了系统的硬件的构成。阐述了利用ST7FMC1K2芯片实现无位置传感器无刷直流电机的三段式起动方法;最后通过实验证明该系统具有较宽的凋速范围、优越的静态和动态特性。此方案电路简单、可靠性高,具有较高的应用价值。     

汽车用永磁无刷直流电机无位置传感器技术研究

研究一种汽车用永磁无刷直流电机无位置传感器控制技术-反电动势三次谐波检测法,它是利用定子反电动势三次谐波积分的方法来估算转子的位置。具体工作过程就是把电枢三相电压进行叠加,然后从中提取出反电动势的三次谐波分量,通过选择其积分过零点为电机的三相逆变电路的换相点。最后通过实验表明其与理论分析完全一致,为其在实际应用提出一种新的方法。     

永磁同步电动机新型滑模观测器无传感器控制

由于传统滑模观测器算法存在固有抖振, 根据永磁同步电动机的数学模型, 设计了一种新的滑动模态观测器转子位置自检测控制算法; 切换函数采用饱和函数代替开关函数; 选择合适的边界层厚度以削弱抖振; 将反电动势估算值反馈到定子电流的观测计算中, 通过选择合适的反馈值来提高低速时转子位置角的估算精度和高速时系统的稳定性. 为了简化驱动系统的硬件结构以提高滤波效果, 设计了一个截止频率可随转子转速变化的低通滤波器对延迟进行补偿. 以1台表面式永磁同步电动机为对象进行实验, 实验结果表明, 这种新型滑模观测器对电机参     

VARIABLE STRUCTURE CONTROL OF TWO MANIPULATORS HANDLING A CONSTRAINED OBJECT

The control of two manipulators handling a constrained object involves the control of the position of the object, the internal force used to grasp the object, and the constraint force due to the constraint surface. The robustness of the controller must be guaranteed when the system faces parameter uncertainties and or external disturbances. In this paper, a variable structure control law is proposed. This controller guarantees the asymptotic convergence of the position of the object, internal force, and constraint force to their desired values when uncertainties on the parameters and external disturbances are present in the system. Simulation results for two planar robots moving an object along a horizontal plane illustrate the fact that the proposed controller achieves the desired asymptotic tracking.     

基于高频注入法的永磁同步电动机无传感器矢量控制

提出了一种在零速或是低速时无传感器的永磁同步电动机矢量控制方法。该方法基于永磁同步电动机的凸极效应原理,在两相旋转坐标系中注入高频信号来获取无传感器矢量控制时所需转子的精确位置和转速,并在此基础上给出了永磁同步电动机无传感器矢量控制系统。仿真结果表明,该方法能够准确估计转子位置和速度,满足矢量控制的需要。     

失重环境下可控柔性臂的模态特性

在非重力场中,考虑控制器动态反馈的影响,对存在控制器定位约束的柔性臂系统进行动力分析,研 究其在相对平衡位置的模态特性．以具有柔性关节和弹性臂杆的可控柔性臂为研究对象,分析了控制器作用下的反 馈约束特性,将控制器位置和速度增益引入力边界条件,得到了耦合控制器参量的模态特征方程,证明了反馈约束 的存在使得系统特征频率为复频率,且模态主振型是复变函数．通过数值仿真,明确了可控柔性臂的模态特性与控 制器增益之间的关系,得到了不同于经典振动理论的结论．设计了可控柔性臂的仿失重实验平台,试验模态结果证 明了理论分析的有效性．     

Complementary compound set-point control by combining muscular internal force feedforward control and sensory feedback control including a time delay

This paper proposes a new set-point control method for a musculoskeletal arm by combining muscular internal force feedforward control with feedback control including a large time delay. The proposed method accomplishes robust and rapid positioning with a relatively small muscular force. In the positioning by the muscular internal force feedforward controller, a large muscular force is required to achieve good performance. On the other hand, in the positioning by the feedback controller including the large time delay, the system can easily fall into an unstable state. A simple linear combination of these two controllers makes it possible to improve the control performance and to overcome the drawbacks of each controller in a complementary manner. First, a two-link six-muscle arm model is considered as a musculoskeletal system in this study. Second, the new set-point control method, which consists of the feedforward control signal and the feedback control signal including the time delay, is designed. Third, the stability of the proposed method is investigated using the Lyapunov–Razumikhin method. Finally, the results of numerical simulations and experiments are presented to demonstrate the advantages of the proposed method.     

Development of a wheeled inverted pendulum mobile platform with a four-bar parallel mechanism

A wheeled inverted pendulum (WIP) offers benefits such as a small floor occupation area, high dynamic stability, and horizontal force sensitivity. However, the body of a WIP robot inclines at the start of acceleration or deceleration, when an external force is applied, or when the position of a CoG is changed. This incline may result in degraded task performance such as object dropping during delivery or image swaying when taking video. In this paper, a WIP mobile platform adopting a four-bar parallel mechanism which provides robust load position variance and horizontal posture keeping is proposed. The basic structure of this platform connects two front and rear inverted pendulums and two upper and lower bars with free-rotational joints, so as to act as a four-bar parallel link mechanism. Based on the features of the parallel mechanism, the platform can maintain a horizontal posture of the upper bar during balancing motion under various disturbances. The motion equations of the mobile platform showed that a change of the loading condition on the upper bar did not affect the balancing characteristics, as confirmed via balancing simulations. Two possible application tasks, namely object delivery and image taking, were successfully demonstrated to show the utility of the platform in terms of its horizontal posture compensation function and its robustness in terms of load position variance.     

Vibrational positioning method for optical fibers sliding on a frictional surface

 Open-loop positioning methods for optical fibers on glass substrates are presented. When a slender and flexible object such as an optical fiber is moved on a frictional surface, its position is difficult to control because the object is caught in a frictional dead zone, causing the occurrence of stick-slip. In this paper, first, a positioning method when the friction force is known is derived based on a one-degree-of-freedom model of a sliding optical fiber. Then, a positioning method when the friction force is not known is derived by modifying the method for the case of known friction. Finally, the validity of the theory is verified by experiment and simulation. Received: 5 July 2001/Accepted: 1 November 2001     

A New Full‐Order Sliding Mode Observer Based Rotor Speed and Stator Resistance Estimation for Sensorless Vector Controlled Pmsm Drives

Sensorless control of a permanent magnetsynchronous motor (PMSM) at low speed remains a challenging task. In this paper, a sensorless vector control of PMSM using a new structure of a sliding mode observer (SMO) is proposed. To remove the mechanical sensors, a full‐order (FO‐SMO) is built to estimate the rotor position and speed of PMSM drives. The FO‐SMO, which replaces a sign function by a sigmoid function, can reduce the chattering phenomenon. In order to overcome time delay, we cancel the low pass filter. This sensorless speed control shows great sensitivity to stator resistance and system noise. To improve the robustness of sensorless vector control, a full‐order SMO technique has been used for stator resistance estimation. A novel stator resistance estimator is incorporated into the sensorless drive to compensate for the effects of stator resistance variation. The validity of the proposed FO‐SMO with a 1.1 kw low‐speed PMSM sensorless vector control is demonstrated by experiments. In this paper, experimental results for FO‐SMO, back‐EMF SMO and MRAS techniques were obtained with fixed point DSP‐based (TMS320F240).     

Robust computationally efficient control of cooperative closed-chain manipulators with uncertain dynamics

This article presents a decentralized control scheme for the complex problem of simultaneous position and internal force control in cooperative multiple manipulator systems. The proposed controller is composed of a sliding mode control term and a force robustifying term to simultaneously control the payload's position/orientation as well as the internal forces induced in the system. This is accomplished independently of the manipulators dynamics. Unlike most controllers that do not require prior knowledge of the manipulators dynamics, the suggested controller does not use fuzzy logic inferencing and is computationally inexpensive. Using a Lyapunov stability approach, the controller is proven to be robust in the face of varying system's dynamics. The payload's position/orientation and the internal force errors are also shown to asymptotically converge to zero under such conditions.