This paper deals with the sliding mode control of a rigid rotor supported by radial magnetic bearings. First, the control law is developed to be robust to external forces caused by the rotor unbalance and transient disturbances. This control law is then discretized for its implementation on a digital computer. Three methods are presented to determine the required coil current for each magnet. Next, an analytical technique has been developed to calculate the steady state amplitudes of the digital closed-loop system. Lastly, results from this analytical technique and numerical simulations are presented for the rotor operating at 30,000 rpm.

In the flexible robot force control situations, if there exists a discontinuity between the robot tip sensor and the work-piece, the robot contact process becomes a nonlinear system control problem. The control tasks require the robot hand to switch from free motion control to contact motion control. The inevitable high impact force tends to let the system become unstable. The purpose of this paper is to investigate the control of the manipulator during this process. In this paper, dynamic models of the flexible link manipulator in both non-contacted and contacted modes are first derived. Due to the fact that the arm vibration shape functions are changed between the two modes, a transform matrix will be used to transform the controlled state variables, such as generalized position and velocity. A nonlinear sliding mode control technique has been implemented in an attempt to extinguish the chatter phenomenon and settle quickly to the desired setpoint.

In this paper, a sliding mode controller is studied in the experimental control of a flexible undamped beam actuated by a DC motor and including Coulomb friction. A model of the system is described which includes a finite element representation for the beam and a representation for Coulomb friction. The model has been used in the study of closed-loop transient response of the slewing system and predicts the critical factors observed in slewing behavior. Development of the sliding mode controller is based on the nonlinear model of the system. The performance and characteristics of the controller are summarized in a simulation study. The sliding mode controller is particularly effective at eliminating the negative effects of shaft lock-up which tends to result from Coulomb friction and counteracts these nonlinear effects in the presence of modeling uncertainties. The system model includes the interaction that occurs between the DC motor and the slewing beam and a gear train that influences the motor-beam interaction. The effect of motor-beam dynamic interaction is studied for the nonlinear slewing system under sliding mode control. It is found that the motor-beam interaction continues to be an important factor in the closed-loop performance. The paper concludes with a summary of experimental results for the nonlinear control of the motor-beam system.

This paper proposes a new sliding mode control method using μ synthesis theory. This concept is based on the frequency-shaped approach. A conventional hyperplane consisits of a desired reference model without dynamics. Therefore, the sliding mode control system becomes often unstable based on spillover phenomena in a higher frequency region. On the other hand, the proposed design method can completely suppress such spillover phenomena because of the frequency-shaped hyperplane. Also, it has good robustness and robust performance in cases of parameter variations on the hyperplane to minimize the maximum singular value and structured sigular value from some noise to the controlled variables. We have just applied this new method to the flexible structure of the miniature test rig with four stories like high rise building. We have verified from simulations and experiments that the new sliding mode control method proposed in this paper has good performances and it is very useful to suppress the spillover in a higher frequency region.

In this paper, a method to realize the motion and vibration control without sensors is proposed. Sensorless control is generally realized by estimating the state of the system from the measured current in the actuator by means of an observer. It is possible to estimate all state variables because of dynamic interaction in the controlled object. Then we realize nonlinear robust control system based on the observer. In this paper, first we formulate sensorless control system. As controlled objects we deal with a multi-degree-of-freedom structure as a vibration control problem and a single link robot arm as a motion control problem, respectively, and we carry out numerical simulations. Moreover, we also verify the possibility of realization of sensorless control by experiments.

An improvement step in robust control is studied for uncertain (linear or nonlinear) systems. The proposed two-stage control scheme first modifies the original desired trajectory, and then imposes robustness against uncertainties in tracking this modified trajectory. For the trajectory modification stage, a simple scheme is considered : time optimal-rigid body motion (TO). The robustness stage is performed using Sliding Mode Control with Perturbation Estimation (SMCPE), an advanced form of SMC. This routine brings some strong features as demonstrated by examples. A rotating hub with flexible beam attachment is taken as the first example, and an undercontrolled two-mass system with a linear spring as the second. The comparative studies show superior results for the combination of TO-SMCPE over the basic SMCPE. Moreover, this two-stage control exhibits stable and highly advantages performance even for cases where H ∞ -type of robust control structure is declared unstable by earlier investigations.

We discuss the sliding mode control to suppress a spillover phenomena caused by truncation of the higher flexible modes for a flexible system. We propose a new method to suppress a higher frequency region including a truncated flexible modes and chattering by filtering control inputs through low-pass filter. And also, we can easily design a control system and apply for an actual system. We have verified from simulations and experiments for flexible structure that the proposed method has good performance and is very useful for spillover suppression.

This study is concerned with design of a sliding mode hyper-plane for a class of linear parameter-varying (LPV) plants whose state-space matrices are affine function of time-varying physical parameters. The proposed hyperplane involving linear matrix in-equality (LMI) approach has continuous dynamics due to scheduling parameters and provide stability and robustness against parametric uncertainties. We have designed gain-scheduled sliding mode hyperplane for a rotor-magnetic bearing system with gyroscopic effect which can be considered LPV plant due to parameter dependence to rotational speed. The obtained hyperplane is continuously scheduled with respect to rotational speed. We successfully carried out experiment using a commercial use turbo-molecular pump system and results were reasonable and good.

This paper dealt with design scheme of sliding mode optimal tracking control in which the hyperplane is designed to follow the desired trajectory without time-delay. At first, we designed the servo system by applying conventional optimal tracking control, H 1 and H ∞ optimal tracking control. Secondly, we show the design method of sliding mode optimal tracking control. Thirdly, we carried out the simulation to verify the validity of the design method. In the simulation, three patterns were examined by using H 2 norm. The trajectory following and the robust performance in the difference of the design methods were clarified by the simulations. Finally, we applied these control methods to a quadruped locomotion robot.

It is considered that locomotion robots are aggressive under the circumstances where human hardly work, for example, in the nuclear power plant, in the bottom of the sea and on a planet. The injury and the fault of the robot might occur frequently under those circumstances. It is very important problem that the robot can realize the walking with the fault. This is very difficult problem for biped and quadruped robot to realize a stable walking in the case that actuator or sensor is broken. And, in walking of mammal, gait pattern is generated by neural oscillator existing in the spinal cord. In the case that a lower neural system is injured, mammal realize a walking by a higher neural system. Thus, mammal has a self renovation function. In this study, in order to realize the stable walking of the quadruped robot with fault, we discuss the control method with self renovation function for the fault of the decentralized controller and the angular sensor. First, we design the centralized controller of one leg by sliding mode control for the fault of decentralized controller. Second, Sky Hook Suspension Control is applied for the fault of the angular sensor. The proposed methods are verified by 3D simulations by CAD and experiments.

Experimental evaluation of the vibration suppression control performance about the output feedback sliding mode controller for the two-link flexible robot arm is presented. The reduce-order controller is designed based on a kind of the component mode synthesis modeling methodology, and is also designed by the combination of the suboptimal output feedback control and the sliding mode control algorithm. From the experiments of the two-link flexible robot arm model, the good agreement between the numerical simulation results and the experimental ones are obtained not only the motion of the joints but also the arm vibration. And it is verified that the presented output feedback sliding mode controller suppresses the vibration of the flexible arm quit well for various attitude.

In this study, we propose the sensorless positioning control of a two-link robot arm. In order to realize a good sensorless control, we propose to use the parameter adaptive identifier to system with the uncertainties of the coil in the actuator. Also, we use sliding mode control theory to remove the terms of the nonlinear parameters generated by the links mechanism, the nonlinear friction in the gear trains in the joints and the parameter variations caused by handle loads. The proposed control strategy has a good robust performance against these uncertainties. As these results, we have verified the effectiveness of sensorless positioning control by simulations and experiments.

Recently, in order to enhance the habitable amenities, passive and active control of structures subjected to weak earthquake and wind response by using tuned mass damper (TMD) has been proposed and has been applied. However, the ordinary tuned mass damper is difficult to control the response of structures under the strong earthquake. This paper deals with the response control of a structure by a tuned mass damper with lever and pendulum mechanism (LP-TMD) under the strong earthquake. We applied sliding mode control method to control the response of the four-degree-of-freedom structure with hysteretic restoring force, and we compared the performance of the sliding mode control system with that of the LQ control system.

The parametric fuzzy sliding mode control (FSMC) and parametric fuzzy neural network control (FNNC) methods, in the present study, is applied to suppress vibration of the axially moving string system, which is driven by adjusting the axial tension. Due to the difficulty of utilizing fuzzy logic control (FLC) to obtain the linguistic control rules, the stability and robustness are not guaranteed. The sliding-mode control is then incorporated in the scheme of FLC to generate the control rule bases in order to meet the requirement of stability and robustness. In additions, for the purpose of improving system performance, the Genetic Algorithm (GA) is applied to search for the optimal parameters of the fuzzy sliding mode controller. Beside the aforementioned method of fuzzy sliding mode control plus GA, the on-line learning algorithm Fuzzy Neural Network (FNN) accompanied with sliding mode characterization is also developed and applied to achieve control goal. In this method, the parameters of FNN are adjusted in the direction that minimizes sliding mode variables SṠ where S of the switching function for vibration suppression. Simulations are conducted to verify the effectiveness of control designs. The results show the performance of FSMC with GA in general is favorable to others.

This paper reports a method for regulating the internal forces during in hand manipulation of an unknown shaped object with soft robotic fingers. It is known that for the case of multifingered manipulation, a part of the forces applied by the fingers result in the motion of the object, whereas the other part is considered to be an internal force. The internal forces do not result in the motion of the object but are used to improve the grip on the object. For an object with unknown shape, the internal forces are regulated to ensure that the object does not slip off during manipulation. It is shown that if soft fingers show bounded conformity and the finger-object interface does not have relative slip (or a bounded slip), then the relative angular velocity between the object and the fingertip frame in contact is bounded. The proof is used to define of a new metric of relative slip. The metric is used to design a sliding mode control algorithm. The robotic fingers are assumed to be under virtual rigidity constraint, that is, the distance between the fingers do not change. The control algorithm is attractive as it skirts requirement of information of the shape of the object or to solve optimization problems. The control algorithm developed controls the internal forces and does not require the knowledge of the shape of the object. The methodology is simulated for the case of one spherical object and one conical object.

This paper studies the chattering-free finite-time control for a class of fractional-order nonlinear systems. First, a class of fractional-order nonlinear systems with external disturbances is presented. Second, a new finite-time terminal sliding mode control method is proposed for the stability control of a class of fractional-order nonlinear systems by combining the finite-time stability theory and sliding mode control scheme. Third, by designing a controller with a differential form and introducing the arc tangent function, the chattering phenomenon is well suppressed. Additionally, a controller is developed to resist external disturbances. Finally, numerical simulations are implemented to demonstrate the feasibility and validity of the proposed method.

This paper is concerned with the ultra high precision tracking control problem of a class of hysteretic systems with both external disturbances and model uncertainties. By integrating a time rate function of the input into the classical Prandtl-Ishlinskii operators, a rate-dependent Prandtl-Ishlinskii model is introduced to compensate the rate-dependent hysteresis of such systems. Furthermore, the resulting inverse compensation error is considered, and a finite-time convergent disturbance observer-based sliding mode control methodology is proposed to improve both the tracking accuracy and transient performance. In this control methodology, a finite-time convergent disturbance observer is employed to estimate various disturbances for accurate eliminations, where the inverse compensation error is regarded as a bounded disturbance. Meanwhile, a novel sliding mode controller is designed to achieve the finite-time stability of the closed-loop system. In particular, it can be proved that both the sliding variable and disturbance estimated error can converge to zero in a finite time. Finally, the proposed control architecture is applied to a PZT (piezoelectric transducer) actuated servo stage, where good hysteresis suppression capability and excellent tracking performance are demonstrated in the experimental results.

The stability and trajectory control of a quadrotor carrying a suspended load with a fixed known mass has been extensively studied in recent years. However, the load mass is not always known beforehand in practical applications. This mass uncertainty brings uncertain disturbances to the quadrotor system, causing existing controllers to have a worse performance or to be collapsed. To improve the quadrotor’s stability in this situation, we investigate the impacts of the uncertain load mass on the quadrotor. By comparing the simulation results of two controllers — the proportional-derivative (PD) controller and the sliding mode controller (SMC) driven by a sliding mode disturbance of observer (SMDO), the quadrotor’s performance is verified to be worse as the uncertainty increases. The simulation results also show a controller with stronger robustness against disturbances is better for practical applications.

This work presents the angular positioning control of a flexible beam like structure connected to the shaft of a DC (Direct Current) motor. The coupling between the flexible structure and the DC motor is considered as not ideal being that the structure model considers three vibration modes. A non-linearity known as death zone is included in the DC motor model. To control the angular position a Sliding mode controller is proposed and the influence of the control gains is analyzed numerically. Numerical simulations will be presented to demonstrate the application of the sliding modes technic in order to control the positioning of the flexible link by controlling the DC motor armor current.

This paper firstly summarizes a newly developed knee joint mechanism of a gait rehabilitation robot, as well as a modified dynamics model for pneumatic muscle actuators (PMAs). The major sections focus on the development of single-input-single-output sliding mode trajectory tracking controller for the knee mechanism. The sliding mode controller takes the models of the whole system, which include the pneumatic flow dynamics of the analogue valves and PMAs, dynamic model of the PMAs and dynamics of the mechanism, into account. It controls the voltage applied to the valves to track desired angular trajectories of the knee joint. The preliminary experiments on the sliding mode controller have been conducted and the results have indicated that the knee mechanism’s successful tracking of sinusoidal waves with frequencies and magnitudes closed to actual human gait. Currently, the researchers are working on the development of multi-inputs-multi-outputs control of the mechanism for both trajectory tracking and compliance adjustments.