Two-wheeled Inverted Pendulum Robot Research Articles

Design and Implementation of a Two-Wheeled Inverted Pendulum Robot With a Sliding Mechanism for Off-Road Transportation

This paper proposes a multi-degrees-of-freedom two-wheeled inverted pendulum robot (mD-TWIPR) for off-road transportation. A two-wheeled inverted pendulum robot (TWIPR), popularly known as a segway, has high mobility owing to its simple structure without steering or suspension. The proposed robot has a car-like structure with a low and elongated body that provides advantages for transporting long objects, such as pipes, or transferring patients on off-road terrain. However, a car-like TWIPR structure faces several challenges, including limited acceleration, difficulty traversing slopes, asymmetric payload, and lower ability to climb steps. To address these issues, we implemented a sliding mechanism in the mD-TWIPR. The proposed mD-TWIPR is designed to move without tilting while carrying movable mass, and tilt the torso according to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$20^{\circ }$</tex-math></inline-formula> slope. It can also maintain stationary on a slope with only a small wheel torque by positioning the center of mass on the fulcrum, which is advantageous for transportation operations. Furthermore, it can climb a step using a combination of the wheel and sliding mechanism. The paper discusses the modeling and design specifications and presents a prototype and experiments to verify the proposed performance of mD-TWIPR.

Balancing-Prioritized Anti-Slip Control of a Two-Wheeled Inverted Pendulum Robot Vehicle on Low-Frictional Surfaces with an Acceleration Slip Indicator

When a two-wheeled inverted pendulum (TWIP) robot vehicle travels on slippery roads, the occurrence of wheel slip extremely threatens its postural stability owing to the loss of wheel traction. If a severe wheel slip happens between the driving wheels and contact surfaces, no control techniques can guarantee the driving performance and stability of the TWIP robots in the absence of an extra wheel slip control strategy. In this paper, a TWIP-compatible countermeasure against the wheel slip phenomena is investigated for enhancing the reliability of the vehicle and the robustness of the motion control performance on low-frictional surfaces. To this end, we propose a balancing-prioritized anti-slip control method based on the maximum transmissible torque estimation, which is activated only when a wheel slip is detected by the acceleration slip indicator utilizing accessible data from the IMU and wheel encoders. It is proved that the TWIP vehicles applying the proposed method can successfully cope with low frictional surfaces while maintaining postural stability. Finally, comparative simulations and experiments demonstrate the effectiveness and feasibility of the proposed scheme.

A Novel LiDAR-IMU-Odometer Coupling Framework for Two-Wheeled Inverted Pendulum (TWIP) Robot Localization and Mapping with Nonholonomic Constraint Factors.

This paper proposes a method to solve the problem of localization and mapping of a two-wheeled inverted pendulum (TWIP) robot on approximately flat ground using a Lidar–IMU–Odometer system. When TWIP is in motion, it is constrained by the ground and suffers from motion disturbances caused by rough terrain or motion shaking. Combining the motion characteristics of TWIP, this paper proposes a framework for localization consisting of a Lidar-IMU-Odometer system. This system formulates a factor graph with five types of factors, thereby coupling relative and absolute measurements from different sensors (including ground constraints) into the system. Moreover, we analyze the constraint dimension of each factor according to the motion characteristics of TWIP and propose a new nonholonomic constraint factor for the odometry pre-integration constraint and ground constraint factor in order to add them naturally to the factor graph with the robot state node on SE(3). Meanwhile, we calculate the uncertainty of each constraint. Utilizing such a nonholonomic constraint factor, a complete lidar–IMU–odometry-based motion estimation system for TWIP is developed via smoothing and mapping. Indoor and outdoor experiments show that our method has better accuracy for two-wheeled inverted pendulum robots.

A novel Stereo-IMU system based on accurate pose parameterization of two-wheeled inverted pendulum (TWIP) robot in localization and mapping

PurposeThis paper aims to propose a method to solve the problem of localization and mapping of a two-wheeled inverted pendulum (TWIP) robot on the ground using the Stereo–inertial measurement unit (IMU) system. This method reparametrizes the pose according to the motion characteristics of TWIP and considers the impact of uneven ground on vision and IMU, which is more adaptable to the real environment.Design/methodology/approachWhen TWIP moves, it is constrained by the ground and swings back and forth to maintain balance. Therefore, the authors parameterize the robot pose as SE(2) pose plus pitch according to the motion characteristics of TWIP. However, the authors do not omit disturbances in other directions but perform error modeling, which is integrated into the visual constraints and IMU pre-integration constraints as an error term. Finally, the authors analyze the influence of the error term on the vision and IMU constraints during the optimization process. Compared to traditional algorithms, the algorithm is simpler and better adapt to the real environment.FindingsThe results of indoor and outdoor experiments show that, for the TWIP robot, the method has better positioning accuracy and robustness compared with the state-of-the-art.Originality/valueThe algorithm in this paper is proposed for the localization and mapping of a TWIP robot. Different from the traditional positioning method on SE(3), this paper parameterizes the robot pose as SE(2) pose plus pitch according to the motion of TWIP and the motion disturbances in other directions are integrated into visual constraints and IMU pre-integration constraints as error terms, which simplifies the optimization parameters, better adapts to the real environment and improves the accuracy of positioning.

Decoupled Multi-Loop Robust Control for a Walk-Assistance Robot Employing a Two-Wheeled Inverted Pendulum

This paper develops a decoupled multi-loop control for a two-wheeled inverted pendulum (TWIP) robot that can assist user’s with walking. The TWIP robot is equipped with two wheels driven by electrical motors. We derive the system’s transfer function and design a robust loop-shaping controller to balance the system. The simulation and experimental results show that the TWIP system can be balanced but might experience velocity drifts because its balancing point is affected by model variations and disturbances. Therefore, we propose a multi-loop control layout consisting of a velocity loop and a position loop for the TWIP robot. The velocity loop can adjust the balancing point in real-time and regulate the forward velocity, while the position loop can achieve position tracking. For walking assistance, we design a decoupled control structure that transfers the linear and rotational motions of the robot to the commands of two parallel motors. We implement the designed controllers for simulation and experiments and show that the TWIP system employing the proposed decoupled multi-loop control can provide satisfactory responses when assisting with walking.

Control of the two-wheeled inverted pendulum (TWIP) robot in presence of model uncertainty and motion restriction

Purpose The purpose of this paper is to improve control performance and safety of a real two-wheeled inverted pendulum (TWIP) robot by dealing with model uncertainty and motion restriction simultaneously, which can be extended to other TWIP robotic systems. Design/methodology/approach The inequality of lumped model uncertainty boundary is derived from original TWIP dynamics. Several motion restriction conditions are derived considering zero dynamics, centripedal force, ground friction condition, posture stability, control torque limitation and so on. Sliding-mode control (SMC) and model predictive control (MPC) are separately adopted to design controllers for longitudinal and rotational motion, while taking model uncertainty into account. The reference value of the moving velocity and acceleration, delivered to the designed controller, should be restricted in a specified range, limited by motion restrictions, to keep safe. Findings The cancelation of model uncertainty commonly existing in real system can improve control performance. The motion commands play an important role in maintaining safety and reliability of TWIP, which can be ensured by the proposed motion restriction to avoid potential movement failure, such as slipping, lateral tipping over because of turning and large fluctuation of body. Originality/value An inequation of lumped model uncertainty boundary incorporating comprehensive errors and uncertainties of system is derived and elaborately calculated to determine the switching coefficients of SMC. The motion restrictions for TWIP robot moving in 3D are derived and used to impose constraints on reference trajectory to avoid possible instability or failure of movement.

CONTROL OF TWO-WHEELED INVERTED PENDULUM ROBOT USING ROBUST PI AND LQR CONTROLLERS

In this paper, a robust PI controller in combination with a linear quadratic regulator (LQR) is proposed to control a two-wheeled inverted pendulum robot (TWIPR) such that it is kept balanced while moving. The proposed TWIPR control system consists of two control loops. The inner loop has two PI controllers for two DC motors’ currents, which are separately designed based on a robust PI controller structure. The outer loop contains a LQR controller for the tilt angle, heading angle and position of the TWIPR. The proposed PI controller is compared to the existing method such as the magnitude optimum (MO) and genetic algorithm (GA) methods. The proposed control scheme is verified through simulations and practical tests, and it is also compared to the MO-LQR and GA-LQR strategies.

선회주행 성능 개선을 위한 양바퀴 역진자 로봇 설계

선회주행 성능 개선을 위한 양바퀴 역진자 로봇 설계

Nonlinear Control of Two-Wheeled Robot Based on Novel Analysis and Design of SDRE Scheme

This brief presents a nonlinear control design for a two-wheeled inverted pendulum robot, based on new analysis of the classical state-dependent Riccati equation (SDRE) scheme and a novel alternative strategy. The solvability of pointwise algebraic Riccati equations (AREs) corresponding to the nonunique state-dependent coefficients (SDCs) of the SDRE scheme is analyzed from a new perspective. This is formulated as a simple equivalence condition with reduced dimensionality, which circumvents the excessive online computational effort to check the solvability of classical SDRE. The condition is derived in a way to facilitate the generalization to all meaningful SDCs. Moreover, due to unsolvable AREs, all conflicts against the primary objective of posture balance of the robot are revealed and illustrated, with a connection to the robot physical parameters. At the system states that cause such conflicts and other unsolvable AREs, a simple analytical solution via alternative SDC constructions is suggested. More potential advantages of this SDC construction over the classical scheme are revealed in simulations, e.g., the maximum input/torque and total energy consumption.

Design of a Networked Controller for a Two-Wheeled Inverted Pendulum Robot

The topic of this paper is to use an intuitive model-based approach to design a networked controller for a recent benchmark scenario. The benchmark problem is to remotely control a two-wheeled inverted pendulum robot via W-LAN communication. The robot has to keep a vertical upright position. Incorporating wireless communication in the control loop introduces multiple uncertainties and affects system performance and stability. The proposed networked control scheme employs model predictive techniques and deliberately extends delays in order to make them constant and deterministic. The performance of the resulting networked control system is evaluated experimentally with a predefined benchmarking experiment and is compared to local control involving no delays.

A MATLAB-based virtual robotics laboratory: Demonstrated by a two-wheeled inverted pendulum

In this paper, a procedure for designing a MATLAB-based virtual robotics laboratory is described that provides a realistic three-dimensional animation for the robot’s motion. The proposed laboratory allows students to obtain the linear model and stability condition of a robotic system, without getting involved in its mathematical modeling. The structure of a two-wheeled inverted pendulum robot has been used for demonstrating the laboratory’s features. As part of this virtual experiment, design and evaluation of proportional–integral–derivative, model predictive control, and fuzzy controllers for maintaining the two-wheeled inverted pendulum’s balance are considered. A set of graphical–user interfaces is designed for providing the interaction with the system. This virtual lab is readily extensible for other robotics structures and controllers, and its output data is promptly available for further analysis by other MATLAB toolboxes.

Nonlinear Optimal Control Design for Underactuated Two-Wheeled Inverted Pendulum Mobile Platform

In terms of the state-dependent Riccati equation (SDRE) control framework, a nonlinear motion control is investigated for the two-wheeled inverted pendulum (TWIP) mobile robot platform. As a critical design issue, the state dependent coefficient matrix is established based on the sound understanding of dynamic characteristics of the TWIP robot. The developed SDRE control solution has the merit of robust posture stabilization when the inverted pendulum robot experiences strong nonlinear behaviors due to abrupt external disturbances.

이륜 역진자 로봇의 제어 시스템 개발을 위한 설계 고려사항

This paper addresses some practical design considerations to build a two-wheeled inverted pendulum (TWIP) robot control system. The first issue is to identify the relationship between the primary parameters of the TWIP robot and the guaranteed stability of the time-delayed control loop. Secondly, the required data update rate and the required sensor/actuator performance are suggested for implementing a real-time digital control system. The final issue is concerned with improving the driving performance by investigating the reliability of the inertial sensor for attitude control and the backlash problem in the transmission mechanism.

A two-wheeled inverted pendulum robot with friction compensation

This paper introduces a method of design and implementation of a two-wheeled inverted pendulum (TWIP) robot with friction compensation. Friction in the drive mechanism is a critical factor of robot self-balancing and affects its performance. The friction parameters are identified based on the dynamic model of the drive mechanism. The dynamics of the whole robot system are obtained by the Lagrangian function method and take the robot drive mechanism friction into account. Sliding mode controllers for self-balancing and yaw motion are designed independently, although the TWIP robot is coupled as a nonlinear system. A low cost but low accuracy gyro and accelerator in consumer electronics grade is adopted to estimate the pitch angle and pitch rate. Using the sensor data from the gyro and accelerator fused with the help of a Kalman filter, the robot body pitch angle is obtained precisely, and these are the key state variables for TWIP control. The effect on the sensor installation location is analysed and corrected with innovation, and the precision of the pose estimation is improved accordingly. Several physical experiments are conducted, and the results demonstrate that the proposed method is effective.

Takagi-Sugeno fuzzy modeling of a two-wheeled inverted pendulum robot

A two wheeled inverted pendulum TWIP mobile robot is an under-actuated mechanical system, which is inherently open-loop unstable with highly nonlinear dynamics. This property attracts the interest ...

State control of a 12 DOF mobile manipulator via centroid feedback

This paper presents a method for controlling the time-varying centroid of a two-wheeled mobile manipulator via centroid feedback. The state control of a two-wheeled mobile manipulator is a typical example of the stable control of a nonlinear time-varying system. Because of the principle of the two-wheeled inverted pendulum robot, when the centroid of the mobile manipulator changes, the state of the mobile manipulator changes. To control the state of the mobile manipulator, the centroid of the mobile manipulator must be kept at a vertical position. The position of the centroid of the mobile manipulator can be obtained in Cartesian space via coordinate transformation. The position data are then fed back to the mobile platform for achieving state control of the mobile manipulator. Through simulations, the centroid feedback control is combined with a basic PD control, which completes the state control of the mobile manipulator. The experimental data demonstrate the effectiveness of the proposed method in achieving state control of a 12 DOF mobile manipulator.

Takagi-Sugeno fuzzy modeling of a two-wheeled inverted pendulum robot

A two wheeled inverted pendulum TWIP mobile robot is an under-actuated mechanical system, which is inherently open-loop unstable with highly nonlinear dynamics. This property attracts the interest of researchers worldwide in recent years. This paper presents the development of a linearized model of the TWIP mobile robot based on its nonlinear dynamical model using Takagi-Sugeno T-S fuzzy modeling technique, which can allow the application of linear control techniques in analyzing and efficiently controlling such under-actuated nonlinear system. The complete nonlinear dynamical equations of motion of the TWIP mobile robot were first derived using Kane's Method. Based on the nonlinear dynamical equations of motion, a T-S fuzzy model of the TWIP robot was then developed using local approximation technique. To validate the proposed model, simulations study was carried out and the results show that the proposed model approximates the original nonlinear TWIP mobile robot in the pre-specified domains to certain degree of accuracy.

Dynamic Analysis of a Nonholonomic Two-Wheeled Inverted Pendulum Robot

As a result of the increase in robots in various fields, the mechanical stability of specific robots has become an important subject of research. This study is concerned with the development of a t...