Gang Zheng

• PhD
• Researcher at National Institute for Research in Computer Science and Control

This paper investigates the robust asymptotic stabilization of a linear time-invariant (LTI) system by static feedback with a static state quantization. It is shown that the controllable LTI system can be stabilized to zero in a finite time by means of nonlinear feedback with a quantizer having a limited (finite) number of values (quantization seed...

In this paper, the formation control problem for unicycle multi-agent systems is considered. The design of a generalized homogeneous leader–follower formation control protocol is studied which shows that such a control protocol can be obtained by “upgrading” from the classical linear control. With this proposed control protocol, a finite-time stabi...

In this paper, the formation control problem is considered for unicycle multi-agent systems whose kinematic models contain some external perturbations. The approach to addressing the problem involves the development of a homogeneity-based leader–follower formation control protocol, which takes into account bounded perturbations. It is shown that su...

Precision operations, such as micro-injection and micro-assembly tasks, require accurate and constant torque output. Compliant constant torque mechanisms (CCTMs) can be considered as a potential alternative due to the characteristic of accurate and constant torque output without the need for complex control algorithms and structures. Therefore, it...

Conventional model-based control for continuum robots is often based on the assumption of Piecewise Constant Curvature (PCC). However, the real motion of the continuum robot is greatly different from the PCC assumption which makes convergence of the control algorithm difficult to meet the requirements of stability and accuracy. In this paper, a rea...

Pipeline is widely deployed in infrastructures, which raises a great demand of pipe-climbing robots to provide pipe-inside inspecting and platform delivery. Soft pipe-climbing robots (SPRs) are intrinsically flexible and able to operate within complex, narrow and curving pipelines more effectively than their rigid counterparts. In the state of the...

Background Endoscopic submucosal dissection (ESD) is an effective treatment for early‐stage gastrointestinal cancers. However, traditional surgical instruments lack accuracy and force‐sensing. Methods A new type of continuum robot for ESD is designed. An accurate static model of the proposed continuum robot is established, considering cases where...

The attitude tracking problem for a full-actuated rigid body in 3D is studied using a system model based on Lie algebra . A nonlinear homogeneous controller is designed to track a smooth attitude trajectory in a finite/fixed time. A global settling time estimate is obtained, which is easily adjustable by tuning the homogeneity degree. The input-to...

This paper deals with the tracking problem for the Unicycle Mobile Robot (UMR) with slippage effects. A homogeneous controller is developed based on a particular cascade control strategy. The robustness of the closed-loop system is studied. The design is essentially based on the canonical homogeneous norm being a Lyapunov function of the system. Th...

This paper develops a homogeneity-based approach to finite/fixed-time stabilization of a linear time-invariant (LTI) system with quantized measurements. A sufficient condition for finite/fixed-time stabilization of multi-input LTI system under state quantization is derived. It is shown that a homogeneous state feedback with a novel logarithmic- lik...

Compliant Mechanisms (CMs) have presented their inherently advantageous properties since the nature of CMs is to utilize elastic deformation of the built-in elementary flexible members to transfer motion, force and energy. To predict the performances of CMs and optimize their designs, modeling CMs turns out to be a major concern in this field, part...

In order to establish the dynamic equations of the rigid-flexible coupled robotic mechanisms with large beam-deformations over the horizontal plane, a thorough modeling technique founded on the virtual work concept has been proposed. Based on the transformed full-actuated model, the predefined-time robust sliding mode control strategy is developed...

Compliant Mechanisms (CMs) have presented its inherently advantageous properties due to the fact that CMs utilize elastic deformation of the elementary flexible members to transfer motion, force and energy. Previously, the classic Euler-Bernoulli beam theory is the most used theory in terms of modeling large beam deflections in CMs. However, it has...

High-precision displacement platforms are of great significance in micro/nanoscale manipulation, ultraprecision manufacturing, biological manipulation, and scanning probe microscopes. This paper presents a novel compliant planar parallelogram mechanism (CPPM) for high-precision translational motion utilizing 8 flexible initially curved beams (ICBs)...

Compliant Mechanisms (CMs) serve as a promising alternative for transferring motion, force and energy compared to rigid mechanisms. The mentioned desired function is achieved by making the most of the elastic deflection of all built-in flexible members in CMs, such as slender straight beams and slender initially curved beams (ICBs). Therefore, accu...

In this paper, we investigate the workspace estimation of soft manipulators controlled via arranged bounded actuators. For this, we implement an interval analysis approach on the mathematical model of the investigated soft robot deduced via the adopted Discrete Cosserat method. The proposed method- ology is validated on several planar and spatial s...

This letter investigates the exterior workspace boundary of a soft robot with a certain configuration controlled by equipped bounded actuators. To achieve this, we implement an optimization-based approach on the studied soft robot which has been modeled by the Finite Element Method (FEM). Finally, we provide numerical simulations of various configu...

Compliant Mechanisms (CMs) have been a hot research spot in recent years due to their distinguished mechanism concept from conventional rigid-body mechanisms: CMs can transfer motion, force and energy only through the deflection of flexible components. Therefore, the accurate and efficient kinetostatic modeling for these elementary flexible compone...

Supplementary video for FEM-based Trajectory Tracking Control of a Soft Trunk Robot.

In this paper, the quadrotor stabilization under time and state constraints is studied. The objective is to design a nonlinear controller under time and state constraint for quadrotor. The nonlinear quadrotor model is built by the Euler-Lagrange approach while ignoring the Coriolis terms, hub moment and force. Based on quadrotor’s dynamic model, a...

This paper investigates event-triggered (ET) observers for output-sampled nonlinear state affine systems (ẋ=A(u)x+b(u)). In particular, the sampling of the system’s output is aperiodic and decided by a designed system performance based event-triggered mechanism (ETM). Under this novel ETM, the global exponential stability of the observer system is...

As a novel class of robots, soft robots have demonstrated many desirable mechanical properties than traditional rigid robots due to their nature of being compliant, flexible and hyper-redundant, such as great adaptability to unknown environments, safe human robot interaction (HRI), energy-saving actuation and the maneuverability to display diverse...

Compliant Mechanisms (CMs) present several desired properties for mechanical applications only depending on elastic deformation of the involved compliant beams/flexures. As reported in the current literature, most CM designs utilize straight beams and initially curved beams (ICBs) as the fundamental flexible members. In CM research community , many...

Compliant Mechanisms (CMs) are used to transfer motion, force and energy, taking advantages of the elastic deformation of the involved compliant members. A branch of special type of elastic phenomenon called (post) buckling has been widely considered in CMs: avoiding buckling for better payload-bearing capacity and utilizing post-buckling to produc...

Considering a soft manipulator configuration, controlled via installed bounded actuators, this paper addresses the end-effector workspace estimation problem for such a soft robot. For this, the Discrete Cosserat method is adopted to deduce the mathematical model of soft manipulators, based on which a continuation method that accounts for simple and...

A procedure of upgrading a linear observer to homogeneous (nonlinear) one is proposed and validated by experiment. The nonlinear observer design is based on the concept of a linear geometric homogeneity. The simple procedure developed to apply the homogeneous nonlinear observer is based on the parameters provided by the linear observer, which is po...

A procedure of upgrading a linear observer to homogeneous (nonlinear) one is proposed and validated by experiment. The nonlinear observer design is based on the the concept of a linear geometric homogeneity. The simple procedure developed to apply the homogeneous nonlinear observer is based on the parameters provided by the linear observer, which i...

This paper investigates the workspace estimation of soft manipulators. Given a configuration of such a soft robot, with the bounded actuators, the Discrete Cosserat method is adopted to deduce the mathematical model of soft manipulators, based on which an optimization-based approach is proposed to estimate the workspace. Implemented to various soft...

Supplementary video for FEM-based Gain-Scheduling Control of a Soft Trunk Robot.

Compliant Mechanisms (CMs) present several desired properties for mechanical designs. Conventional rigid-body mechanisms composed of rigid links connected at kinematic joints, serve as devices to transfer motion, force and energy by the movements of rigid links whereas CMs are able to present the same function only through deflection of flexible me...

This book presents a differential geometric method for designing nonlinear observers for multiple types of nonlinear systems, including single and multiple outputs, fully and partially observable systems, and regular and singular dynamical systems. It is an exposition of achievements in nonlinear observer normal forms. The book begins by discussin...

Soft robotics has recently become an emergent research area due to its unique characteristics compared to conventional rigid robots. Its inherent properties, such as compliance and flexibility, provide some promising characteristics for the current robotic applications, including safe human machine interaction, great adaptability to unknown environ...

In this chapter, we present a study of the observability problem of a general class of linear time-delay systems affected by unknown inputs. We give two different notions of observability. The unknown input observability (UIO) allows us to reconstruct the trajectories of the system by using past, present, and future values of the system output, or...

It is of importance to design observers for multi‐variable non‐linear systems with unknown parameters and partially driven by unknown inputs. Such a problem arises in systems subject to disturbances or with inaccessible inputs and in many applications such as parameter identification, fault detection and isolation or cryptography. In this study, th...

In this paper, we investigate the observation and stabilization problems for a class of linear time-invariant systems, subject to unknown states, and network constraints, including time-delays and event-triggered sampling. A new type of event-triggered mechanism is proposed based on an appropriate storage function, which is chosen larger than the d...

A procedure for an “upgrade” of a linear proportional‐integral‐differential (PID) controller to a nonlinear homogeneous one is developed and verified by real experiments with quadrotor. The controller design is based on a generalized homogeneity (dilation symmetry) of the system. Its parameters are obtained from the gains of linear controller. The...

In this article, an observer‐based adaptive boundary iterative learning control law is developed for a class of two‐link rigid‐flexible manipulator with input backlash, the unknown external disturbance, and the endpoint constraint. To tackle the backlash nonlinearities and ensure the vibration suppression, the disturbance observers based upon the i...

In this paper, we address the challenge of sensor fusion in Soft Robotics for estimating forces and deformations. In the context of intrinsic sensing, we propose the use of a soft capacitive sensor to find a contact's location, and the use of pneumatic sensing to estimate the force intensity and the deformation. Using a FEM-based numerical approach...

Soft robotics is an emergent research field which has variant promising applications. However, the design and control of soft robots nowadays still suffer from the inefficient trial-and-error process. To eliminate the drawback, this paper proposes an innovative simulation/control co-design methodology for designing soft robotics. The main idea is t...

Soft robot is an emergent research field which has variant promising applications, and the control of such robots is still challenging. Unlike using different techniques (such as Beam theory, Cosserat theory or high dimensional finite-element method) to model the dynamics of soft robots, this paper introduces a simplified nominal model with uncerta...

A novel scheme for an "upgrade" of a linear control algorithm to a non-linear one is developed based on the concepts of a generalized homogeneity and an implicit homogeneous feedback design. Some tuning rules for a guaranteed improvement of a regulation quality are proposed. Theoretical results are confirmed by real experiments with the quadrotor Q...

This paper investigates the event-triggered observer design problem for nonlinear state affine systems. The output data of systems are event-triggered-sampled (sparse) and received by observer with certain time delays. A novel event-triggered mechanism is proposed to decide when the data need to be transmitted. The proposed observer globally and ex...

This paper deals with the robust controller design problem to regulate the position of a soft robot with elastic behavior, driven by 4 cable actuators. In this work, we first used an artificial neural network to approximate the relation between these actuators and the controlled position of the soft robot, based on which two types of robust control...

It is well-known that observer design is a powerful tool to estimate the states of a dynamical system. Given a multi-output nonlinear dynamical system whose states are partially observable, this paper investigates the problem of observer design to estimate those observable states. It considers firstly a nonlinear system without inputs, and provides...

In this paper, we introduce a new pneumatic mechanosensor dedicated to Soft Robotics and propose a generic method to reconstruct the magnitude of a contact-force acting on it. Changes in cavity volumes inside a soft silicon pad are measured by air-flow sensors. The resulting mechanosensor is characterized by its high sensitivity, repeatability, dyn...

Arising in a large number of application areas, sparse recovery (SR) has been exhaustively investigated and many algorithms have been proposed. Different from the numerical methods realized by iterative algorithm, the recent continuous approach is realized through analog circuit, which takes advantage of short time-delay and fast convergence. Howev...

The problem of a state feedback design for control of a quadrotor system under state and time constraints is studied. Convex embedding approach and Implicit Lyapunov function are employed to design a finite-time controller. The feedback gain is solved by a system of LMIs(Linear Matrix Inequalities). Theoretical results are supported with numerical...

This paper presents the robust controller design for an indoor blimp robot to achieve application such as the surveillance. The commonly used 6 degrees of freedom dynamic model is simplified under reasonable assumptions and decoupled into two independent parts. The blimp simplified horizontal plane movement model is complemented with disturbance te...

Comparison of several types of differentiation algorithms has been performed in the paper Wang, Zheng, Efimov, and Perruquetti [(2018). Differentiator application in altitude control for an indoor blimp robot. International Journal of Control, 1–10. Retrieved from https://doi.org/10.1080/00207179.2018.1441549] with application to a robotic blimp al...

This paper proposes a fixed-time differentiator running in parallel with a feedback linearisation-based controller, which allows quadrotors to track a given trajectory. The fixed-time differentiator estimates outputs’ derivatives in a predefined convergence time, largely compensating for initial condition problems and solving the delay problem. Com...

In this paper we investigate the left invertibility problem for a class of nonlinear time-delay systems. In both cases of time delay systems with and without internal dynamics the invertibility conditions are given. A new approach based on the use of higher order sliding mode observer is developed for finite-time left invertibility and for asymptot...

This paper presents design of altitude controller with disturbance compensation for an indoor blimp robot and its realisation. Due to hardware restrictions, the altitude control behaviour of blimp is modelled as a switched system with a constant time-delay complemented with uncertain bounded disturbances. In order to achieve state estimation, four...

This paper presents a fixed-time observer for a general class of linear time-delay systems. In contrast to many existing observers, which normally estimate system's trajectory in an asymptotic fashion, the proposed observer estimates system's state in a prescribed time. The proposed fixed-time observer is realized by updating the observer in an imp...

This paper presents a new method to design observers for linear time-delay systems with unknown inputs both in the state and the output. In contrast to many observers, which normally estimate the system state in an asymptotic fashion, the proposed observer estimates the exact system state in a predetermined finite time. The finite-time observation...

This paper deals with the observability problem of a sort of singular systems with commensurate time-delays in the trajectories of the system, in the time derivative of the trajectories (neutral terms), and in the output system. By using a recursive algorithm, sufficient conditions (easy testable) are proposed for guaranteeing the backward and the...

In this paper a general class of linear systems with time-delays is considered, which includes linear classical systems, linear systems with commensurate delays, neutral systems and singular systems with delays. After given a formal definition of functional backward observability (BO), an easily testable condition is found. The fulfillment of the o...

This paper deals with delay identifiability and delay estimation for a class of nonlinear time-delay systems. The theory of non-commutative rings is used to analyze the identifiability. In order to estimate the delay, a sliding mode technique and a classical Newton method are combined to show the possibility to have a local (or global) delay estima...

This paper presents a finite-time observer for linear time-delay systems with commensurate delay. Unlike the existing observers in the literature which converge asymptotically, the proposed observer provides a finite-time estimation. This is realised by using the well-known homogeneous technique, and the results are also extended to investigate the...

This paper considers the problem of attitude and altitude control of quadrotors using the sliding mode control theory. The mathematical model of the quadrotor is derived using the Euler-Newton formalism with extended assumptions on disturbing aerodynamical forces (not necessary uniformly bounded). The proposed control demonstrates an enhanced robus...

Even though Sparse Recovery (SR) has been successfully applied in a wide range of research communities, there still exists a barrier to real applications because of the inefficiency of the state-of-the-art algorithms. In this paper, we propose a dynamical approach to SR which is highly efficient and with finite-time convergence property. Firstly, i...

This paper investigates the problem of the state reconstruction for LTI systems with time-delayed outputs. The proposed observer allows the reconstruction of the states in two steps. In the first step, an impulsive observer provides an estimation of the delayed states. In the second step, the actual states is estimated by the second observer using...

This paper considers the problem of attitude and altitude control of quadrotors using the sliding mode control theory. The mathematical model of the quadrotor is derived using the Euler-Newton formalism with extended assumptions on disturbing aerodynamical forces (not necessary uniformly bounded). The proposed control demonstrates an enhanced robus...

This paper presents design of altitude controller for an indoor blimp robot and its realization. Due to hardware restrictions, the altitude control behavior of blimp is modeled as a switched system with time-varying delay. HOSM differentiator is used as an observer for vertical velocity, it is also used in order to estimate the switching signal. Th...

This paper investigates the problem of the state reconstruction for LTI systems with time-delayed outputs. The proposed observer allows the reconstruction of the states in two steps. In the first step, an impulsive observer provides an estimation of the delayed states. In the second step, the actual states is estimated by the second observer using...

In this paper, a fault-tolerant control scheme for two physically linked two wheel drive (2WD) mobile robots with multiple and simultaneous actuator faults is proposed. The kinematic and dynamic models are first presented. A kinematic control law is designed, based on which, a dynamic control law is investigated. By applying the proposed dynamic co...

This paper investigates observer design problem for a large class of nonlinear singular systems with multi outputs. We firstly regularize the singular system by injecting the derivative of outputs into the system. Then differential geometric method is applied to transform the regularized system into a simple normal form, for which a Luenberger-like...

In this paper, the problem of output control for linear uncertain systems with external perturbations is studied. First, it is assumed that the output available for measurement is only the higher-order derivative of the state variable, instead of the state variable itself (for example, the acceleration for a second-order plant), and the measurement...

This paper investigates the problem of observer design for a general class of linear singular time-delay systems, in which the time delays are involved in the state and its derivatives, the output and the known input (if there exists). The involvement of the delay could be multiple which however is rarely studied in the literature. Sufficient condi...

This paper presents a new approach to estimate states and parameters of the permanent magnet synchronous motor (PMSM) in the presence of unknown load torque disturbance. Indeed, it highlights an auxiliary dynamics that is added to the PMSM model. Thereby, it supplies a change of coordinates that transforms the extended model (PMSM model together wi...

This study presents a new approach to estimate states and parameters of the permanent magnet synchronous motor (PMSM) in the presence of unknown load torque disturbance. Indeed, it highlights an auxiliary dynamics that is added to the PMSM model. Thereby, it supplies a change of coordinates that transforms the extended model (PMSM model together wi...

This paper aims at designing a non-asymptotic fractional order differentiator for a class of fractional order linear systems to estimate the Riemann-Liouville fractional derivatives of the output in discrete noisy environment. The adopted method is a recent algebraic method originally introduced by Fliess and Sira-Ramirez. Firstly, the fractional d...

The problem of avoiding obstacles while navigating within an environment for a Unicycle-like Wheeled Mobile Robot (WMR) is of prime importance in robotics; the aim of this work is to solve such a problem proposing a perturbed version of the standard kinematic model able to compensate for the neglected dynamics of the robot. The disturbances are con...

It is well-known that, for nonlinear systems, the observability is often only a local property and depends on the input. Moreover, it is often required that the observer be of the same dimension as the original system. A direct consequence of this requirement is that it enlarges the set of observability singularities. If, on one hand, it is impossi...

This paper investigates observer design problem for a large class of nonlinear singular systems with multi outputs. We firstly regularize the singular system by injecting the derivative of outputs into the system. Then differential geometric method is applied to transform the regularized system into a simple normal form, for which a Luenbergerlike...

In this paper, a model-free–based terminal sliding-mode control (MFTSMC) strategy is developed to control the attitude and position of a quadrotor whose model includes parameter variations, uncertainties, and external disturbances. The proposed MFTSMC combines a model-free control approach with a sliding-mode technique and makes possible to elimina...