Stable Position Tracking Research Articles

Observer-based adaptive dynamic sliding mode control for automatic clutch position tracking

The automatic clutch’s precise and stable position tracking is critical in automated manual transmission, significantly influencing vehicle performance. Clutch position control is challenging due to directly unmeasurable clutch output position, nonlinear characteristics, parameter uncertainties, and external disturbance of the automatic clutch system. This paper proposes an observer-based adaptive dynamic sliding mode control strategy to overcome these obstacles to the clutch position tracking process. The extended state observer (ESO) introduced in the designed strategy handles total disturbance, including nonlinearities and uncertainties for feedback control and total compensation. A sigmoid tracking differentiator arranges the transient process and smooth approach signal for the reference input and its differential signal. An adaptive dynamic sliding mode controller acts as the primary feedback control to realize fast and precise position tracking of the automatic clutch system based on the signal from ESO. Simulation and hardware-in-loop (HIL) experimental tests verify the effectiveness and advantage of the proposed control strategy for the clutch position tracking performance in the face of parameter perturbation and external disturbance, for example, the root mean square value of static tracking error of the designed strategy is 14.9% and 24.7% lower than that of ESO-based sliding mode control and robust sliding mode control strategy in the HIL test, respectively.

Anti-disturbance fault-tolerant control with flexible performance for combined spacecraft attitude tracking under limited thrusts

This paper proposes a novel anti-disturbance fault-tolerant control scheme for prescribed performance attitude tracking of combined spacecraft equipped with thrusters. In practice, the output magnitude of each thruster is limited. When severe actuator faults and/or strong disturbances occur, the remaining active thrusters under limited thrusts may not provide sufficient actuating torques to ensure the satisfaction of prescribed performance. To fill this gap, a tactfully constructed auxiliary system is introduced to generate a series of modification signals, whereby the performance envelops can be actively relaxed when the commanded inputs exceed the thrust limits, while recovering to the nominal level when input saturations disappear. With the modified performance functions (MPFs), a robust adaptive controller is designed to achieve stable attitude tracking of combined spacecraft with flexible performance. Stability analysis shows that the proposed controller can ensure that both the attitude and angular velocity tracking errors evolve strictly within the MPFs, and that all closed-loop signals are uniformly ultimately bounded, despite the presence of external disturbances, thruster faults, and input saturation. Finally, simulation results are provided to show the effectiveness of the proposed method.

Fault detection and isolation based on space projection operator for hypersonic re-entry vehicles with concurrent actuator faults

This article investigates fault detection, isolation and fault-tolerant control for an over-actuated system in hypersonic re-entry vehicle with concurrent actuator faults and disturbance. A series of residuals developed by spatial projection operators is only sensitive to certain faults that can decouple the effects of faults in different directions. Threshold intervals designed through sliding-time windows and a hypothesis test are used to detect faults. Single and concurrent fault isolation can be achieved by utilizing different residual combinations. Subsequently, an augmented observer is introduced to estimate the faults and satisfies the [Formula: see text]-gain constraint to reduce the effect of disturbances. Finally, an adaptive backstepping fault-tolerant control algorithm is designed to achieve stable attitude tracking. The stability of the proposed schemes is proved by Lyapunov and linear matrix inequality theories. Numerical simulation results demonstrate the effectiveness of the proposed methods.

Composite Control of Attitude Tracking and Vibration Suppression of a Rigid–Flexible Coupled System

AbstractThis paper presents a composite control approach that facilitates both stable attitude tracking and vibration suppression of a space flexible slewing truss. An improved proportional-differe...

Investigations on system integration method and dynamic performance of electromechanical actuator.

A highly integrated electromechanical actuator was developed in this article, which aims at fulfilling the requirements of high power-to-weight ratio, high efficiency, high integration and low volume in military equipment. Three different transmission schemes were proposed for the integrated electromechanical actuator according to the differences in integration methods. Comparative analysis was conducted on the specific structures of the integrated electromechanical actuator and the categories and performance of the planetary roller screw, which is the key unit of the integrated electromechanical actuator. An integrated electromechanical actuator was designed based on the project requirements. A mathematical model was established and the system transfer function was derived. Based on this, a simulation model of the position loop system was established using the AMESim software and the effects of some related parameters, such as friction, backlash and stiffness, on the dynamic performance of the system were investigated. The related theory and simulation results were experimentally validated by a self-developed integrated electromechanical actuator research prototype combined with the related test system. The data obtained from the step response tests, sinusoidal response tests and repeat locating accuracy tests indicated that the developed integrated electromechanical actuator prototype is of rapid, accurate and stable position tracking capability.

Fault-Tolerant Prescribed Performance Attitude Tracking Control for Spacecraft Under Input Saturation

This brief examines the problem of attitude tracking control with prescribed performance guarantees for a spacecraft subjected to actuator faults and input saturation. To pursue this, the open-loop tracking error dynamics with certain designer-specified performance constraints is first transformed into an equivalent “state-constrained” one, via an error transformation; furthermore, the resulting dynamics is augmented with a dynamic system, which is tactfully constructed to ensure that the control input satisfies the magnitude limits. Subsequently, a robust fault-tolerant controller is developed by using a low-pass filter and an auxiliary system in conjunction with adaptive backstepping design. It is shown that the control algorithm developed not only achieves the stable attitude tracking with prescribed behavioral metrics but also guarantees the boundedness of all the closed-loop signals. Finally, simulation results are given to evaluate the efficacy of the proposed scheme.

Adaptation Mechanism of Asymmetrical Potential Field Improving Precision of Position Tracking in the Case of Nonholonomic UAVs

SummaryPosition-tracking problems in the structures of rigid formations of nonholonomic mobile robots, such as fixed-wing unmanned aerial vehicle (UAVs), must reconcile tracking precision and flight stability, which usually exclude each other due to nonholonomic motion constraints. Therefore, a position-tracking control that is based on distance and position displacement, defined as inputs of control loops, requires the application of dead zones around target positions, which are the points of instability. For this reason, the control becomes sensitive to any external disturbance causing oscillations of control signals and so it becomes difficult to maintain a zero value of position displacement over a long time horizon. Thus, we propose an approach based on the adaptive mechanism of an asymmetrical local artificial potential field, which is defined by a local frame of reference whose origin is located in the tracked position of a UAV in the formation frame. It couples controls of both airspeed and heading angle into a nonlinear potential function of relative position and orientation with respect to the tracked position and adapts it according to heading rate of the leader. The function splits the area around the tracked position longitudinally into two zones of acceleration and deceleration; therefore, velocity vectors are longer (higher airspeed) only when a UAV is behind the tracked position and shorter (lower airspeed) when it is ahead. The area is laterally symmetrical, and orientations of velocity vectors align asymptotically to the longitudinal direction accordingly with the decrease in the lateral error. Finally, velocity vectors are rotated proportionally to the heading rate of the leader, which improves the tracking precision during turns. If we assumed that a UAV’s tracked position is in motion, it could easily be proven that the position control based on the adaptive asymmetrical potential function becomes asymptotically stable in the tracked position. Numerical simulation verifies this thesis and presents more precise and stable position tracking due to the adaptation mechanism.

Spacecraft attitude manoeuvre using robust generalised dynamic inversion

This paper presents the design of rigid body spacecraft attitude control using robust generalised dynamic inversion (RGDI). In RGDI control, the particular part is responsible to enforce the constraint dynamics based on the attitude deviation function. The control law is extracted by inverting the prescribed constraint dynamics using Moore-Penrose generalised inverse (MPGI). The auxiliary part of the RGDI control which is affine in the null space of the control coefficient vector is utilised to stabilise the angular body rates. The singularity problem is addressed by augmenting the dynamic scale factor in MPGI. To guarantee robustness against parametric variations and disturbances, an additional term based on the concept of sliding mode control is integrated with GDI, such that semi-global practically stable attitude tracking is guaranteed. The RGDI controller's performance is evaluated through numerical simulations on the spacecraft mathematical model whose kinematical and dynamical equations are modelled in Simulink/MATLAB environment.

Autonomous Underwater Vehicles Attitude control using Neuro-Adaptive Generalized Dynamic Inversion

A novel two loops control architecture is presented for motion control of Autonomous Underwater Vehicle (AUVs). The outer (slow) positional loop incorporates classical Proportional-Derivative control to generate reference pitch and yaw tilting commands based on the positional errors. The reference attitude commands are fed to the inner (fast) attitude control loop, which utilizes Neuro-Adaptive Generalized Dynamic Inversion (NAGDI) control to generate the elevator and rudder deflections. The baseline Generalized Dynamic Inversion (GDI) control composed of particular and auxiliary parts. The particular part is designed by dynamically scaled generalized inversion of the attitude error dynamics, and the auxiliary part is constructed via a Lyapunov control function to provide global asymptotic stability to the angular body rate dynamics. A discontinuous control based on the concept of Sliding Mode Control (SMC) theory is augmented with baseline GDI. The modulation gain of discontinuous term is made adaptive to avoid chattering. Furthermore, online estimation of the unknown nonlinear attitude dynamics is achieved through radial basis function neural networks to obtain the resultant NAGDI control law. The proposed control law guarantees semi-global practically stable attitude tracking. Computer simulations are conducted on a six degrees of freedom simulator of the Monterey Bay Aquarium Research Institute AUV under nominal and perturbed marine environments.

Launch vehicle ascent flight attitude control using direct adaptive generalized dynamic inversion

This paper presents the attitude control design of satellite launch vehicle based on the direct adaptive generalized dynamic inversion approach. The proposed adaptive generalized dynamic inversion approach encompasses the equivalent and the adaptive control elements. The equivalent (continuous) control part of adaptive generalized dynamic inversion is based on the conventional generalized dynamic inversion approach that comprises two noninterfering control actions, i.e. the particular part and the auxiliary part. In the particular part, dynamical constraint is prescribed in the form of time differential equation, which is evaluated along the vehicle attitude trajectories that encapsulates the control objectives and is inverted by utilizing Moore Penrose Generalized Inverse (MPGI). The singularity problem is solved by augmenting a dynamic scaling factor in the involved MPGI. In the auxiliary part, the null control vector is designed using the proportionality gain matrix, constructed by employing the Lyapunov function that guarantees global closed-loop asymptotic stability of the angular body rate dynamics. The adaptive (discontinuous) control part of adaptive generalized dynamic inversion is based on the sliding mode control with adaptive modulation gain, that provides robustness against tracking performance deterioration due to generalized scaling, system nonlinearities, and uncertainties, such that semi-global practically stable attitude tracking is guaranteed. External guidance loop based on the trajectory following method is designed, which reshapes the predefined pitch and yaw attitude profiles based on the respective normal and lateral positional errors, for acquiring the desired orbital parameters such as height, injection angle, orbital velocity, etc. To analyze the ascent flight trajectory, a detailed six-degrees-of-freedom simulator of a four-stage satellite launch vehicle is developed. The intensive numerical simulations are performed, which demonstrate the stability, robustness and the tracking capability of the proposed control and guidance methods in the presence of parametric uncertainties and external disturbances.

Robust generalized dynamic inversion based control of autonomous underwater vehicles

A novel two-loop structured robust generalized dynamic inversion–based control system is proposed for autonomous underwater vehicles. The outer (position) loop of the generalized dynamic inversion control system utilizes proportional-derivative control of the autonomous underwater vehicle’s inertial position errors from the desired inertial position trajectories, and it provides the reference yaw and pitch attitude angle commands to the inner loop. The inner (attitude) loop utilizes generalized dynamic inversion control of a prescribed asymptotically stable dynamics of the attitude angle errors from their reference values, and it provides the required control surface deflections such that the desired inertial position trajectories of the vehicle are tracked. The dynamic inversion singularity is avoided by augmenting a dynamic scaling factor within the Moore–Penrose generalized inverse in the particular part of the generalized dynamic inversion control law. The involved null control vector in the auxiliary part of the generalized dynamic inversion control law is constructed to be linear in the pitch and yaw angular velocities, and the proportionality gain matrix is designed to guarantee global closed-loop asymptotic stability of the vehicle’s angular velocity dynamics. An additional sliding mode control element is included in the particular part of the generalized dynamic inversion control system, and it works to robustify the closed-loop system against tracking performance deterioration due to generalized inversion scaling, such that semi-global practically stable attitude tracking is guaranteed. A detailed six degrees-of-freedom mathematical model of the Monterey Bay Aquarium Research Institute autonomous underwater vehicle is used to evaluate the control system design, and numerical simulations are conducted to demonstrate closed-loop system performance under various types of autonomous underwater vehicle maneuvers, under both nominal and perturbed autonomous underwater vehicle system’s mathematical model parameters.

Nonlinear adaptive control for dynamic and dead-zone uncertainties in robotic systems

Accurate position tracking performance of robotic systems with both dynamic and dead-zone uncertainties is difficult to achieve by traditional adaptive control. In this paper, for nonlinear robotic systems in the presence of uncertain dynamics and dead-zone, an adaptive control scheme is employed to guarantee accurate and stable position tracking. The dynamics of the robot and dead-zone parameters are concurrently estimated in the adaptation laws and the estimated values are subsequently applied in the control law. In order to demonstrate the practicability of this paper, an experimental setup composed of Phantom Omni robots are built. The experimental results show that even when the dynamic and dead-zone uncertainties simultaneously appear, the robot can well track any desired position trajectory.

A Global Tracking Controller for Underactuated Aerial Vehicles: Design, Analysis, and Experimental Tests on Quadrotor

This paper investigates the global tracking control of underactuated aerial vehicles. In particular, the globally exponentially stable attitude tracking controller serving as the inner loop of the overall controller is investigated. It can avoid the common problems that may be accompanied by other attitude controllers, such as singularity and unwinding. In order to overcome the topological obstacles of global control on $SO(3)$ , rotational motion of a rigid body is expressed in the exponential coordinate restricted in a compact domain. We then construct a hybrid tracking error dynamics whose states are all represented in Euclidean space. The geometric properties of the state space are mathematically analyzed. The tracking controller of underactuated aerial vehicles is, thus, designed based on the hybrid tracking error dynamics. The global exponential stability of the closed-loop attitude subsystem, as well as the global asymptotical stability of the closed-loop overall system under assumptions, is analyzed using Lyapunov's method strictly. These properties are demonstrated by simulation results. The proposed controller is also implemented and tested on our self-developed quadrotor, showing the feasibility of the controller in realtime applications.

A Hybrid Haptic Sensation for Teleoperation of Hydraulic Manipulators

In this paper, a control scheme is designed for stable haptic teleoperation of hydraulic manipulators. The controller results in a stable position tracking for the hydraulic actuator (slave) in both unconstrained and constrained motions. The force feedback at the haptic (master) side is a combination of two different sensations. For free motion, the haptic device provides a haptic force based on the position error between the displacements of the master and the slave. The force also serves to alert the operator when the slave is ahead or behind in position tracking of the master. Once the slave comes in contact with the environment, the haptic force is augmented by the interaction force. The uniqueness, continuation, and existence of the Filippov solution to this system with the discontinuity surfaces are proven first. The extension of Lyapunov's stability theory to nonsmooth systems is then employed to prove the stability by constructing a Lyapunov function. The effectiveness of the controller is validated via experimental studies. It is shown that while stable, the system performs well in terms of position tracking of the hydraulic actuator and providing a haptic feel to the operator. The measurements required by the controller are supply pressure, actuator's line pressures, interaction force, and displacements of the master and slave.

Generalized Dynamic Inversion Scheme for Satellite Launch Vehicle Attitude Control

This paper presents a generalized dynamic inversion attitude control design for satellite launch vehicle. Dynamic constraints that encapsulate the attitude tracking objectives are prescribed in the form of asymptotically stable differential equations in the attitude variables deviations from their reference trajectories. The constraint differential equations are evaluated along the vehicle's attitude trajectories and are inverted to solve for the control variables using the Greville formula for underdetermined algebraic systems. The associated null control vector is constructed using Lyapunov stability principle, and a delaying dynamic scaling factor is augmented in the involved Moore-Penrose generalized inverse for assured singularity avoidance and stable attitude tracking. The effectiveness of the proposed control scheme is shown by its evaluation on a 6DOF model of a satellite launch vehicle in the presence of various external disturbances.

Robust Adaptive Neural-Fuzzy Network Tracking Control for Robot Manipulator

This paper presents a robust adaptive neural-fuzzy network control (RANFNC) system for an n-link robot manipulator to achieve the highprecision position tracking. Initially, the model dynamic of an n-link robot manipulator is introduced. However, it is difficult to design a conformable model-based control scheme, for instance, external disturbances, friction forces and parameter variations. In order to deal with this problem, the RANFNC system is investigated to the joint position control of an n-link robot manipulator. In this control scheme, a four-layer neural-fuzzy-network (NFN) is used for the main role, and the adaptive tuning laws of network parameters are derived in the sense of a projection algorithm and the Lyapunov stability theorem to ensure network convergence as well as stable control performance. The merits of this model-free control scheme are that not only the stable position tracking performance can be guaranteed but also unknown system information and auxiliary control design are required in the control process. The simulation results are provided to verify the effectiveness of the proposed RANFNC methodology.

Lyapunov stable displacement-mode haptic manipulation of hydraulic actuators: theory and experiment

In this article, a stable control scheme is designed and experimentally evaluated for haptic-enabled teleoperated control of hydraulic actuators. At the actuator (slave) side, the controller allows the hydraulic actuator to have a stable position tracking. At the master side, the haptic device provides a kind of ‘feel’ of telepresence to the operator by creating a force that acts like a virtual spring, coupling the displacement of the haptic device to the displacement of the hydraulic actuator. In free motion, this virtual spring restricts the operator's hand to move fast when the slave manipulator is behind/ahead in terms of tracking the master manipulator's displacement. On the other hand, when interacting with the environment, the constrained force imposed on the hydraulic actuator is indirectly reflected through this virtual spring force. Extension of Lyapunov's stability theory to non-smooth systems is first employed to prove the stability of the resulting control system. Effectiveness of the controller is then validated via experimental studies. It is shown that the control scheme performs well in terms of both positioning the hydraulic actuator and providing a haptic feel to the operator. The control scheme is easy to implement since very little knowledge about system parameters is needed and the required on-line measurements are actuator's supply and line pressures and displacement.

Self-organizing adaptive neural fuzzy control for electrically driven robot manipulators

A novel self-organizing adaptive neural fuzzy control (SANFC) is proposed for the trajectory tracking of an n -link robot manipulator including motor dynamics. In this control scheme, a self-organizing neural fuzzy network (SONFN) is constructed simultaneously to estimate online the system uncertainties with the structure and parameter learning phases. The fuzzy rules in the SONFN can be either generated or eliminated to obtain a suitable-sized network structure, and the adaptive tuning laws of network parameters are derived in the sense of the Lyapunov synthesis approach to ensure network convergence as well as stable control performance. A supervisory controller is used to attenuate the effects of the approximation error on the tracking error. The merits of the SANFC are that not only can the stable position tracking be achieved but also a suitable-sized network structure is found to avoid overfitting or underfitting data sets. Experiments performed on a two-link robot manipulator driven by direct current servomotors demonstrate the effectiveness of the scheme.

Robust Neural-Fuzzy-Network Control for Robot Manipulator Including Actuator Dynamics

This paper addresses the design and analysis of an intelligent control system for an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex> -link robot manipulator to achieve the high-precision position tracking. According to the concepts of mechanical geometry and motion dynamics, the dynamic model of an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex> -link robot manipulator including actuator dynamics is introduced initially. However, it is difficult to design a suitable model-based control scheme due to the uncertainties in practical applications, such as friction forces, external disturbances, and parameter variations. In order to deal with the mentioned difficulties, a robust neural-fuzzy-network control (RNFNC) system is investigated to the joint position control of an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex> -link robot manipulator for periodic motion. In this control scheme, a four-layer neural fuzzy network (NFN) is utilized for the major control role, and the adaptive tuning laws of network parameters are derived in the sense of a projection algorithm and the Lyapunov stability theorem to ensure network convergence as well as stable control performance. The merits of this model-free control scheme are that not only can the stable position tracking performance be guaranteed but also no prior system information and auxiliary control design are required in the control process. In addition, numerical simulations and experimental results of a two-link robot manipulator actuated by dc servo motors are provided to verify the effectiveness and robustness of the proposed RNFNC methodology.