A Novel Prescribed-Performance Path-Following Problem for Non-Holonomic Vehicles

The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlled vehicle.In this context,a novel form of the prescribed performance guiding vector field is introduced,accompanied by a prescribed-time sliding mode con-trol approach.Furthermore,the interdependence among the pre-scribed parameters is discussed.To validate the effectiveness of the proposed method,numerical simulations are presented to demonstrate the efficacy of the approach.

Multi-circular formation control with reinforced transient profiles for nonholonomic vehicles:A path-following framework

This article investigates a multi-circular path-following formation control with reinforced transient profiles for nonholonomic vehicles connected by a digraph.A multi-circular formation controller endowed with the feature of spatial-temporal decoupling is devised for a group of vehicles guided by a virtual leader evolving along an implicit path,which allows for a circumnavigation on multiple circles with an anticipant angular spacing.In addition,notice that it typically imposes a stringent time constraint on time-sensitive enclosing scenarios,hence an improved prescribed performance control(IPPC)using novel tighter behavior boundaries is presented to enhance transient capabilities with an ensured appointed-time convergence free from any overshoots.The significant merits are that coordinated circumnavigation along different circles can be realized via executing geometric and dynamic assignments independently with modified transient profiles.Furthermore,all variables existing in the entire system are analyzed to be convergent.Simulation and experimental results are provided to validate the utility of suggested solution.

Visual object-oriented application for lane following on intelligent highway system

A visual object-oriented software for lane following on intelligent highway system (IHS) is proposed. According to object-oriented theory, 3 typical user services of self-check, transfer of human driving and automatic running and abnormal information input from the sensors are chosen out. In addition, the functions of real-time display, information exchanging interface, determination and operation interweaving in the 3 user services are separated into 5 object-oriented classes. Moreover, the 5 classes are organized in the visual development environment. At last, experimental result proves the validity and reliability of the control application.

MICROPROCESSOR BASED MODEL FOLLOWING ADAPTIVE CONTROL SYSTEM FOR CSIM DRIVES

A model following adaptive control system for CSIM is presented in this paper. A dynamic mathematical model of slip control based system is obtained. With the help of model reducing technique, full order model is reduced to simplify the design without degrading much of the performance. Model following adaptive control laws in discrete form are derived. These laws satisfy the hyperstability condition for taking care of the load and machine parameter changes of the drive. A microprocessor 8098 is used to develop the speed controller. The implementation of the control system uses only available variables of the reference model and the controlled plant. Experimental results are given to demonstrate the good performance of the system.

Adaptive sliding-mode path following control system of the underactuated USV under the influence of ocean currents

The path-following control of the asymmetry underactuated unmanned surface vehicle(USV) under external disturbances such as unknown constant and irrational ocean currents is discussed, and an adaptive sliding-mode path-following control system is proposed, which comprises a path-variable updated law,a modified integral line-of-sight(ILOS) guidance law based on a time-varying lookahead distance and adaptive feedback linearizing controllers combined with sliding-mode technique. A more accurate USV model without the assumption of having diagonal inertia and damping matrices is first presented, aiming at improving the performance of the path-following control. Next, the coordinate transformation is adopted to decouple the sway dynamic from the rudder angle, and the path-following errors dynamics without non-singular problem are presented in the moving Frenet-Serret frame. Then, based on the cascaded theorem and the adaptive sliding-mode method, the adaptive control law of position errors and course error are designed, among which the lookahead distance and integral gain are all computed as different functions of cross-track error to estimate and compensate the sideslip angle caused by external disturbances adaptively. Finally, according to the Lyapunov and cascaded theorem, the control system proposed is proved to be uniform globally asymptotic stability(UGAS) and uniform semiglobal exponential stability(USGES) when the control objectives are all achieved. Simulation results illustrate the precision and high-quality performance of this new controller.

Path Following Control of A Deep-Sea Manned Submersible Based upon NTSM

In this paper, a robust path following control law is proposed for a deep-sea manned submersible maneuvering along a predeterminated path. Developed in China, the submersible is underactuated in the horizontal plane in that it is actuated by two perpendicular thrusts in this plane. The advanced non-singular terminal sliding mode （NTSM） is implemented for the design of the path following controller, which can ensure the convergence of the motion system in finite time and improve its robustness against parametric uncertainties and environmental disturbances. In the process of controller design, the close-loop stability is considered and proved by Lyapunov＇ s stability theory. With the experimental data, numerical simulations are provided to verify the control law for path following of the deep-sea manned submersible.

A Mode-Switching Motion Control System for Reactive Interaction and Surface Following Using Industrial Robots

This work proposes a sensor-based control system for fully automated object detection and exploration(surface following) with a redundant industrial robot. The control system utilizes both offline and online trajectory planning for reactive interaction with objects of different shapes and color using RGBD vision and proximity/contact sensors feedback where no prior knowledge of the objects is available. The RGB-D sensor is used to collect raw 3D information of the environment. The data is then processed to segment an object of interest in the scene. In order to completely explore the object, a coverage path planning technique is proposed using a dynamic 3D occupancy grid method to generate a primary(offline) trajectory. However, RGB-D sensors are very sensitive to lighting and provide only limited accuracy on the depth measurements. Therefore, the coverage path planning is then further assisted by a real-time adaptive path planning using a fuzzy self-tuning proportional integral derivative(PID)controller. The latter allows the robot to dynamically update the 3D model by a specially designed instrumented compliant wrist and adapt to the surfaces it approaches or touches. A modeswitching scheme is also proposed to efficiently integrate and smoothly switch between the interaction modes under certain conditions. Experimental results using a CRS-F3 manipulator equipped with a custom-built compliant wrist demonstrate the feasibility and performance of the proposed method.

Coordinated control between a grid forming inverter and grid following inverters suppling power in a standalone microgrid

Battery energy storage systems,fuel cells,and photovoltaic generators are being adopted in distribution networks to achieve CO;emission reduction.These power sources require inverters to connect to AC networks.However,sub-networks,such as a microgrids containing inverter power sources,may be disconnected from the utility network and operated in a standalone mode during extended blackouts.This study focuses on a standalone microgrid supplied by inverter power sources without a synchronous generator and proposes a new microgrid inverter control.In this inverter control,a single grid forming inverter is operated as a master power source to determine frequency and voltage,and other inverters,called grid following inverters,are operated as subordinate power sources with active and reactive power control.The necessary functions in the energy management system are examined,and the coordinated operation of all inverters in the microgrid is demonstrated via simulation.

PREDICTIVE CONTROL FOR OPTIMAL PATH TERRAIN FOLLOWING SYSTEM

In this paper output predictive algorithm is applied to the design of predictive controller for an optimal path terrain following system. In this way, the error of path tracking is decreased to a minimum degree simply and efficiently and the computation time for the optimal path is shortened greatly. Therefore, the real-time processing of the optimal path terrain following system is made to be very helpful.

Finite-Time Sideslip Differentiator-Based LOS Guidance for Robust Path Following of Snake Robots

This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance method are proposed to counteract sideslip drift caused by cross-track velocity.The proposed differentiator can accurately observe the cross-track error and sideslip angle for snake robots to avoid errors caused by calculating sideslip angle approximately.In our method,the designed piecewise auxiliary function guarantees the finite-time stability of position errors.Secondly,for the case of external disturbances and state constraints,a Barrier Lyapunov functionbased backstepping adaptive path following controller is presented to improve the robot’s robustness.The uniform ultimate boundedness of the closed-loop system is proved by analyzing stability.Additionally,a gait frequency adjustment-based virtual velocity control input is derived to achieve the exponential convergence of the tangential velocity.At last,the availability and superiority of this work are shown through simulation and experiment results.

Constrained Moving Path Following Control for UAV With Robust Control Barrier Function

This paper studies the moving path following(MPF)problem for fixed-wing unmanned aerial vehicle(UAV)under output constraints and wind disturbances.The vehicle is required to converge to a reference path moving with respect to the inertial frame,while the path following error is not expected to violate the predefined boundaries.Differently from existing moving path following guidance laws,the proposed method removes complex geometric transformation by formulating the moving path following problem into a second-order time-varying control problem.A nominal moving path following guidance law is designed with disturbances and their derivatives estimated by high-order disturbance observers.To guarantee that the path following error will not exceed the prescribed bounds,a robust control barrier function is developed and incorporated into controller design with quadratic program based framework.The proposed method does not require the initial position of the UAV to be within predefined boundaries.And the safety margin concept makes error-constraint be respected even if in a noisy environment.The proposed guidance law is validated through numerical simulations of shipboard landing and hardware-in-theloop(HIL)experiments.

LSTM-DPPO based deep reinforcement learning controller for path following optimization of unmanned surface vehicle

To solve the path following control problem for unmanned surface vehicles(USVs),a control method based on deep reinforcement learning(DRL)with long short-term memory(LSTM)networks is proposed.A distributed proximal policy opti-mization(DPPO)algorithm,which is a modified actor-critic-based type of reinforcement learning algorithm,is adapted to improve the controller performance in repeated trials.The LSTM network structure is introduced to solve the strong temporal cor-relation USV control problem.In addition,a specially designed path dataset,including straight and curved paths,is established to simulate various sailing scenarios so that the reinforcement learning controller can obtain as much handling experience as possible.Extensive numerical simulation results demonstrate that the proposed method has better control performance under missions involving complex maneuvers than trained with limited scenarios and can potentially be applied in practice.

Design of Wiener-Hopf optimal controller and its application in terrain following system

state space algorithms are proposed for the three degree of freedom (3DOF) optimal Wiener Hopf controller for a class of systems with time delay feedback sensors and employed in the design of a terrain following control system, with the influence caused by the delay of baric altimeter successfully eliminated.

An Application of Optimal Preview Control in Terrain Following System

An optimal preview method is applied to the design of terrain following controller for cruise missile. In this method, tracking errors and control increments are both considered in the quadratic cost function. Integrating the general optimal servo system with a preview feedforward compensation that feeds forward future command and future disturbance produces an optimal preview servo system. In the terrain following system, the flight altitude of the cruise missile is a command signal, and its future information can be known apriori. Hence, we have designed a terrain following controller with a basic state feedback and a feedforward compensation for future altitude information. Simulation results show that the performance of the terrain following system with such an optimal preview controller has been improved dramatically.

Enhancing of nominal characteristic trajectory following control for motion systems

The goal of this paper is to enhance a practical nominal characteristic trajectory following(NCTF) controller that is specifically designed for two-mass point-to-point positioning systems. A nominal characteristics trajectory contained in the NCTF controller acts as movement/motion reference and a compensator is utilized to force the object to detect and follow the reference/desired trajectory. The object must follow and track closely and should be as fast as possible. The NCTF controller is designed with two different intelligent based compensator approaches which are fuzzy logic and extended minimal resource allocation network. The proposed controller which is NCTF are compared with the conventional proportional integral compensator. Then the results of simulation are discussed for the positioning performances. The inertia variations due to the effect of the design parameters are also assessed to see the robustness of controllers. The results show that the NCTF control method designed from an intelligent based compensator has a better positioning performance in terms of percentage of overshoot, settling time, and steady state error than the classical based compensator.

Leader-following consensus control for networked multi-teleoperator systems with interval time-varying communication delays

We study the leader-following consensus stability and stabilization of networked multi-teleoperator systems with interval time-varying communication delays. With the construction of a suitable Lyapunov–Krasovskii functional and the utilization of the reciprocally convex approach, novel delay-dependent consensus stability and stabilization conditions for the systems are established in terms of linear matrix inequalities, which can easily be solved by various effective optimization algorithms. One illustrative example is given to illustrate the effectiveness of the proposed methods.

State Predictive Model Following Control System for Linear Time Delays

In this paper, we propose a new state predictive model following control system （MFCS）. The considered system has linear time delays. With the MFCS method, we obtain a simple input control law. The bounded property of the internal states for the control is given and the utility of this control design is guaranteed. Finally, an example is given to illustrate the effectiveness of the proposed method.

Electro-acupuncture for STAT3 expression and nuclear translocation in hippocampal tissues of rats following cerebral ischemia/reperfusion

BACKGROUND: It has been found in recent years that STAT3 widely distributes in nervous system, including hippocampal CA1-3 region, dentate gyrus and cerebral neocortex, etc. Ischemic brain injury can cause the release of some cytokines and growth factors, while electro-acupuncture may have multi-level, multi-channel and multi-target protective and interventional effects on ischemic brain injury. OBJECTIVE: To observe the effects of electro-acupuncture on STAT3 expression and nuclear translocation in hippocampal CA1 region of rat models of brain ischemia/reperfusion. DESIGN: Randomized and controlled observation. SETTING: Staff Room of Acupuncture and Moxibustion, Department of Acupuncture and Bone Injury, Hubei College of Traditional Chinese Medicine; Tongji Medical College, Huazhong University of Science and Technology. MATERIALS: Seventy-two healthy SD rats, of clean degree and either gender, weighing (200±20) g, were provided by the Experimental Animal Center of Hubei College of Traditional Chinese Medicine. STAT3 monoclonal antibody was purchased from Santa Cruz Company, USA, and G-6805 electro-acupuncture instrument was purchased from Shanghai Medical Electronic Instruments Factory. METHODS: This experiment was carried out in the comprehensive laboratory of Department of Acupuncture and Bone Injury, Hubei College of Traditional Chinese Medicine between September 2005 and February 2006. Seventy-two rats were randomly divided into 4 groups: ① control group(n =6): Untouched. ② Sham-operation group (n =18): Artery was isolated, but without inserting thread bolt.③ Model group (n =24): Rat models of local brain ischemia/reperfusion were established with modified suture occlusion. ④Electro-acupuncture group (n =24): Dazhui and bilateral Neiguan points were selected for electro-acupuncture treatment. No. 28 acupuncture needle of 3.33 cm was used in the treatment. A G-6085 electro-acupuncture instrument with continuous wave, frequency of 120 times/min, intensity of 1 mA, 30 min/time, was used. Acupuncture was conducted firstly at ischemia/reperfusion 3 hours, then once every 12 hours. STAT3 positive nuclear translocation in hippocampal CA1 region of rats was observed with immunohistochemical method at 24, 48 and 72 hours after brain ishcemia/reperfusion, and then STAT3 positive cells were counted. MAIN OUTCOME MEASURES: STAT3 positive cells and nuclear translocation in hippocampal CA1 region of rats in each group. RESULTS: All the 72 rats were involved in the result analysis. ①In the control group and sham-operation group, STAT3 positive cells with light cytoplasm and nucleus were decreased , and nuclear translocation was not found. ② In the model group, STAT3 positive cells were mostly found in the cytoplasm of the hippocampal CA1 region at the ischemic side of rats after ischemia/reperfusion 24 hours. They were significantly more than those in the sham-operation group and control group [(18.00±2.68), (9.00±1.35), (8.00±1.22) cells/ mm2, P < 0.01], but cells with nuclear reaction were fewer; At ischemia/reperfusion 48 and 72 hours, STAT3 positive cells were increased, and they were significantly more than those of sham-operation group [(25.00±3.23), (35.00±3.52) cells/mm2, (13.00±1.93), (12.00±1.24) cells/mm2, P < 0.01]. Positive cells with nuclear reaction were found dark-stained. ③At ischemia/reperfusion 24, 48 and 72 hours, STAT3 positive cells were strongly expressed in hippocampal CA1 region at ischemic side of rats of electro-acupuncture group, and they were significantly more than those of model group [(25±3.52), (50±6.31), (75±8.09) cells/mm2, P < 0.01]. STAT3 positive cells were gradually enhanced with time, and considerable STAT3 nuclear positive reaction cells were found. CONCLUSION: Electro-acupuncture can activate STAT3 protein expression in hippocampal tissue of rats with local brain ischemia/reperfusion, promote STAT3 nuclear translocation and function its neuroprotective effect.

Changes in hemeoxygenase-1 and superoxide dismutase in the peri-hematomal brain tissues of rats following intracerebral hemorrhage

BACKGROUND: The mechanism of intracerebral hemorrhage (ICH)-induced hemorrhagic brain injury is very complicated, involving the position-occupying effect of cephalophyma, ischemic factors, the toxic effect of hematoma components, the destruction of blood-brain barrier, etc. The expression and effect of hemeoxygenase-1 (HO-1) in the cerebrovascular disease has been paid close attention. OBJECTIVE: To observe the expression of HO-1 and change of superoxide dismutase (SOD) in the peri-hematomal brain tissue of rats following ICH. DESIGN: Randomized controlled animal experiment. SETTING: Department of Neurology, Yijishan Hospital Affiliated to Wannan Medical College. MATERIALS: Forty healthy male SD rats, of clean grade, weighing from 250 to 300 g, were provided by Qinglongshan Animal Farm of Nanjing. The involved 40 rats were randomized into sham-operation group (n =5) and ICH group (n =35), and ICH group was divided into 7 subgroups with 5 rats in each: ICH 6, 12, 24, 48, 72, 100 and 168 hours groups. Rabbit anti-rat HO-1 immunohistochemial kit ( Boster Co., Ltd., Wuhan) and SOD kit (Jiancheng Bioengineering Institute, Nanjing)were used in this experiment. METHODS: This experiment was carried out in the Department of Neurology, Yijishan Hospital Affiliated to Wannan Medical College Between April and July 2005. In the ICH group: Autologous blood of rats was injected into the head of caudate nucleus to create ICH animal models. In the sham-operation group, the same amount of normal saline was injected into the head of caudate nucleus of rats. The brains of rats in each group were harvested at different time points. The hematoma-side brain tissue was cut open in the coronal plane taking hematomal region as center, and the posterior part was fixed with 100 g/L neutral formaldehyde. 100 mg brain tissue was taken from anterior part. The number of positive cells in HO-1 and SOD activity in peri-hematomal brain tissue at different time after ICH were detected by immunohistochemical method and xanthine oxidation method respectively. MAIN OUTCOME MEASURES: ① The expression of HO-1 in the peri-hematomal brain tissue of rats in two groups following ICH.② The expression of SOD activity in the peri-hematomal brain tissue of rats in two groups following ICH. RESULTS: ①The number of HO-1 positive cells in the peri-hematomal brain tissue of rats in two groups following ICH 6, 12, 24, 48, 72, 120 and 168 hours was (11.03±2.01),(16.47±2.98),(25.50±5.65),(51.57±7.05),(47.33±4.73),(26.57±5.12),(7.63±2.17) cells/high-fold visual field , respectively; The number of HO-1 positive cells in the ICH 12-120 hours groups was significantly higher than that of sham-operation group [(6.07±1.85)cells/high-fold visual field, P < 0.01]; The HO-1 positive cells were the most in the ICH 48 hours group and were still expressed a little in the ICH 168 hours group. ② The SOD in the brain tissue of rats at ICH 6, 12, 24, 48, 72, 120 and 168 hours was (404.46±8.14),(396.84±10.97),(387.74±5.32),(356.21±9.27),(307.95±10.15),(357.48±11.28) and (402.98±7.23) kNU/g, respectively; The SOD activity of ICH 12 to 120 hours groups was significantly lower than that of sham-operation group [(415.47±11.44) kNU/g,P < 0.01], and that of ICH 72 hours group was the lowest. There was no significant difference of SOD activity between ICH 168 hours group and sham-operation group (P > 0.05). CONCLUSION: Following ICH, the expression of HO-1 in peri-hematomal brain tissue of rats in two groups is obviously increased, but the antioxidant ability of brain tissue is decreased. The changes of both maybe play an important role in the formation of ICH-induced hemorrhagic brain injury.

Mouse-Sensitive Following Path Suggestion for Drawing Travel Routes in Web Map Systems

This paper proposes a web map system for drawing an arbitrary travel route using a mouse-sensitive following path suggestion. The interaction model of the system allows users to intuitively understand the sequence of user actions needed to draw a conceived route and reduces the number of user actions required. Moreover, the system allows users to understand at a glance several drawing alternatives (static suggestion) and also consider a particular drawing alternative (dynamic suggestion) without making any commitment. The proposed architecture of the system reduces the influence caused by communication delay between a map server and a web client by delivering in advance road network data from a map server to a web client. Experimental evaluations on a prototype we developed demonstrated that the proposed system enables users to draw arbitrary routes within noticeably less clicks, in less time, and with less stress than previous systems.