Coaxial Wheels Research Articles

Low energy consumption traction control for centralized and distributed dual-mode coupling drive electric vehicle on split ramps

Distributed drive electric vehicle has good pass ability on split ramps, but it has high power demand for driving motors, resulting in low driving efficiency and limited economy. To address the aforementioned deficiencies, a centralized and distributed dual-mode coupling drive system (DMC) capable of drive force transfer between coaxial wheels is designed to avoid single-side wheel high-intensity driving and reduce vehicle energy consumption. To guarantee the longitudinal dynamics performance, a traction control based on online sliding mode extremum search (SES) was proposed, and the traction control based on the ρ_SES algorithm as a means to suppress the controller damage caused by the steady-state oscillation has also been adopted. The simulation and experiment results show that the dual-mode coupling drive electric vehicle significantly reduces the energy consumption and reduces the power demands of the drive motor than those of the distributed drive electric vehicle. Apparently, the ρ_SES algorithm based traction control suppresses the steady-state oscillations of the SES, which can protect the motor controller. This study lays the theoretical foundation for the use of DMC and achieving superior traction control for electric vehicles.

A computer vision-assisted method for identifying wheel loads of moving vehicles from dynamic bridge responses

Bridge weigh-in-motion (BWIM) technology, which identifies traffic information such as the axle weights, wheelbases, and velocities of vehicles passing over a bridge from bridge responses, can be beneficial for bridge design, management, and maintenance. However, conventional BWIM methods simplified the coaxial wheel loads of a vehicle using one concentrated force, commonly known as the axle load. Such simplification would lead to two problems. Firstly, it fails to calculate the wheel weights of moving vehicles, which are essential for evaluating the service status of roads and is required to be measured by national weigh-in-motion specifications, such as ASTM E1318-09. Secondly, the transverse distance between the coaxial wheels (track width), and unequal load distributions between left and right coaxial wheels (unbalance) were ignored in the conventional BWIM methods. However, these two factors represented the actual characteristics of the vehicle load applied on the bridge. Hence, ignoring these two factors could lead to significant errors in estimating the vehicle weight when the track width or the unbalance ratio of the test vehicle was different from that of the calibration vehicle. To address the above two problems, this study proposed a new BWIM method, where two concentrated loads with fixed transverse distance were used to represent the coaxial wheel loads of the truck in analyzing the interactions between the truck and the bridge. By doing so, the wheel weights of moving vehicles can be calculated, and both the effects of the unbalance and the track width can be considered in estimating the axle weights of the vehicle. Both experiment results and simulation results demonstrated that the proposed method can effectively identify the wheel weights of moving vehicles, and provide more accurate axle weights than conventional BWIM methods under complex traffic scenarios.

Genuine Influence Line and Influence Surface Identification from Measured Bridge Response Considering Vehicular Wheel Loads

A bridge influence line (BIL) and a bridge influence surface (BIS) reflect the relationship between the bridge responses and the loads on the bridge and have been commonly used in techniques such as bridge damage detection, bridge safety evaluation, bridge model correction, bridge weigh-in-motion, and so on. Conventionally, a BIL can be extracted from the bridge response under a moving vehicle with known axle loads, while a BIS can then be obtained by lateral interpolation from BILs obtained for key transverse positions. However, in the traditional BIL-extracting methods, the transverse distance between the coaxial wheels was not considered; that is, the coaxial left and right wheel loads are simply treated as one concentrated load (usually referred to as the axle load). Therefore, the obtained BIL is the bridge response under two loads rather than one. Hence, errors may be introduced to the obtained BILs and propagated to the interpolated BIS. Moreover, the potentially significant effect of the unbalance of coaxial wheel loads on BIL identification is ignored. In this research, a new method for determining a genuine BIL and BIS is proposed. The wheel load rather than the axle load was taken into calculation in this method, where the effect of the transverse distance between the coaxial wheels and the unbalance of the coaxial wheel loads was naturally taken into consideration. Laboratory experiments and numerical simulations were performed to verify the effectiveness of the proposed method. Furthermore, a comprehensive parametric analysis was conducted to investigate the effects of some important parameters such as vehicle velocity, lateral deviation of the center of gravity of vehicles, axle count, and road surface condition on the identification performance. The results show that the BIL and BIS can be identified with satisfactory accuracy.

Position control of a wheel-based miniature magnetic robot using neuro-fuzzy network

AbstractUntethered small-scale robots can accomplish tasks which are not feasible by conventional macro robots. In the current research, we have designed and fabricated a miniature magnetic robot actuated by an external magnetic field. The proposed robot has two coaxial wheels and one magnetic dipole which is capable of rolling and moving on the surface by variation in the direction of magnetic field. To generate the desired magnetic field, a Helmholtz electromagnetic coil is manufactured. To steer the robot to the desired position, at first the robot dynamics is investigated, and subsequently a controller based on a neuro-fuzzy network has been designed. Finally, the proposed controller is implemented experimentally and the performance of the control system is demonstrated.

Steady-State Motion of a Balancing Robot with Two Coaxial Deformable Wheels

At present, the theory of wheeled robotic systems is being actively developed. In modeling the motion of wheeled robots, one mostly uses the classical nonholonomic motion model, which does not take into account the slip of deformable wheels. Meanwhile, for robots with deformable wheels, nonholonomic models can be inadequate for the design and analysis of control algorithms. This can be the case for statically unstable balancing robots with coaxial wheels, similar in design with such vehicles as Segway. Thus, modeling the motion of a two-wheeled robot taking into account the possibility of wheels slip and analysis of applicability of simplified models are of interest. Such models can be used to develop new control algorithms in active maneuvering, and for preliminary estimates of robustness of algorithms designed using approximate nonholonomic models. This paper focuses on modeling the motion of balancing robots, on analyzing their steady-state motion, and on possibilities of their stabilization. It is shown that for models with deformable wheels in the steady-state motion the body has a forward pitch. Such a pitch is not found in most nonholonomic models.

Development and Implementation of a Wheeled Inverted Pendulum Vehicle Using Adaptive Neural Control with Extreme Learning Machines

A novel neural control on basis of extreme learning machines (ELMs) is proposed to control wheeled inverted pendulum vehicle, which is a human transportation platform mounted on two coaxial wheels. A dynamic self-balancing control scheme for such vehicle is constructed which depends on the single-hidden layer feedforward network approximation capability of combing ELMs to capture vehicle dynamics. It is superior to conventional intelligent control by using extreme learning machines since the proposed neural control adjusts the output weight parameters online on basis of the Lyapunov synthesis approach. Experimental results are provided to demonstrate that the vehicle can maintain upright posture stably with the external disturbances based on the proposed control scheme.

Parallel Bicycles and Their Applications

This paper describes the successful research and development (R&D) of parallel bicycles (PB robots) including six prototypes created by the authors and their applications to personal vehicles. The first, developed in 1986, consists of a pair of coaxial wheels and an inverted pendulum on the wheel axis. Since then, the authors have carried out fundamental and practical studies on static/dynamic posture stabilization control, dynamic movement, and slope and stair ascent/descent. The PB robot control mechanism has recently been applied to educational robots, mobile humanoid robots, and personal vehicles. This paper also discusses personal vehicles commercialized as an application of the PB robots.

Theoretical Research on Ideal Brake Force Distribution of Tractor-Semitrailer Cornering Braking

For tractor-semitrailer, load transfer during cornering braking caused big difference of the vertical load between coaxial wheels. As a result, braking efficiency and directional stability were affected seriously, the traditional design of braking force distribution between axles couldnt meet the requirements. In this paper, a dynamic model of tractor-semitrailer was established according to the motion and force during cornering braking. The rule of vertical load changing of each wheel with longitudinal acceleration and lateral acceleration was obtained. Combining with the tire and road adhesion conditions, the ideal brake force distribution was achieved. The research could provide theoretical reference to better control strategy of tractor-semitrailer braking control system.

The Transmission Design of a Human Powered SAGWAY

In this study, a double-wheel self balanced unicycle is proposed. Because of the shortage of energy resource and parking space in city, the idea of this light-weight electrical aid personal unicycle can hopefully be used in future transportation system. The unicycle has the features of small longitudinal length, with two coaxial wheels and pedal by human with electric control system to balance the unicycle. It is known that when the rider rides the unicycle, the paddle force disturbs the balance of the vehicle. This unbalance force comes from the gravity center is not at the point of the ground contact points of the vehicle. To balance the unbalance force, two servo-motors to drive the two wheels are used. The unbalance condition is detected by sensors. A transmission mechanism to combine human power and electric power is designed. Planetary gear set is considerable to be the basic concept of transmission mechanism design. The sequence of study processes would be helpful to design the layout of the transmission about chassis, bike frame, and wheels. The mechanism design could link up the mechanical system with the motors and electro-control system.

The Design and Implementation of a Wheeled Inverted Pendulum Using an Adaptive Output Recurrent Cerebellar Model Articulation Controller

A novel adaptive output recurrent cerebellar model articulation controller (AORCMAC) is utilized to control wheeled inverted pendulums (WIPs) that have a pendulum mounted on two coaxial wheels. This paper focuses mainly on adopting a self-dynamic balancing control strategy for such WIPs. Since the AORCMAC captures system dynamics, it is superior to conventional CMACs in terms of efficient learning and dynamic response. The AORCMAC parameters are adjusted online using the dynamic gradient descent method. The learning rates of the AORCMAC are determined using an analytical method based on a Lyapunov function, such that system convergence is achieved. The variable and optimal learning rates are derived to achieve rapid tracking-error convergence. A WIP standing control is utilized to experimentally verify the effectiveness of the proposed control system. Experimental results indicate that WIPs can stand upright stably with external disturbances via the proposed AORCMAC.

Mobile robots with two independent coaxial drive wheels: Dynamics and the schemes of control

A two-wheeled robot and a robot composed of a snakelike chain of two-wheeled objects are considered. The problem of trajectory synthesis and the problem of motion planning and control are studied for these mobile robots. The mobile robots with two independently controlled coaxial wheels and with one or several passive wheels are called robots with differential drive. These problems are formulated in such a way that the construction of dynamically correct and precise control becomes possible for such robots.

Non-stabilization Structural Mobile Robot with Duplex Modes

Two-wheeled non-stabilization structural mobile robot has the features of differential-driven and coaxial wheels. By real-time stabilizing control method, the robot has advantage of high maneuverability, which can maintain the balance on slopes and rough terrain and can pivot around the central axis of its body in narrow spaces. Mechanical design, dynamic modeling and stabilizing control method of this type of mobile robot platform are discussed. Furthermore the characteristics of its kinematics and dynamics at loaded case on different terrains are explained. The motion posture can be controlled on the basis of the motion balance mode of robot. This prototype is designed to be a light weight, compact size, low consumption platform, and it can be carried by one person. A multi modal control system is developed which includes human transport and goods transport control system modes. In human transport mode, the master controller receives the data from the data conditioning module and generates the reference for controllers while in goods transport mode the master controller receives command from the teleoperator. Through the simulation research, it is shown that the robot can be confirmed as mobile platform for transporting human and goods. The effectiveness of the robot is confirmed by experiments such as climbing slope, pivoting around, surpassing small obstacles, balance standing and human transporting.

An Innovative Drive for Wheeled Mobile Robots

Introduced In this work is an innovative drive for wheeled mobile robots, that is based on two identical, coaxial wheels, independently driven by two identical motors. The common axis is capable of rotating about a vertical axis. The drive, termed dual-wheel transmission (DWT), is composed of two identical epicyclic gear trains, lying at two different levels and coupled by a common planet carrier. The latter can turn freely with respect to the robot platform carrying the motors, the transmission having as a stand-alone unit, three degrees of freedom and only two motors, which makes it underactuated. Upon coupling this drive with two other wheel units, which is the minimum required for static support, a robot with mobility of three is produced with the underactuation thereby disappearing. Finally, the dimensioning of the DWT is reported for robustness against manufacturing, actuation, and sensing errors.

A non-linear predictive control scheme for nonholonomic mobile robots

This paper addresses the problem of closed-loop position control and trajectory tracking of nonholonomic unicycle-type mobile robots with visual-based navigation. The robot focused here has two coaxial wheels, each one driven by an independent DC-motor. The control problem is solved by a Nonlinear Model Based Predictive Controller (NLMBPC) which contains some modifications in order to deal with the system characteristics and improve its tracking behavior. Stability properties of the closed loop system are analyzed and a comparison with a linear MBPC is presented. An actual nonholonomic robot platform, the Khepera robot, is used to validate the proposed strategy.

JOE: a mobile, inverted pendulum

The Industrial Electronics Laboratory at the Swiss Federal Institute of Technology, Lausanne, Switzerland, has built a prototype of a revolutionary two-wheeled vehicle. Due to its configuration with two coaxial wheels, each of which is coupled to a DC motor, the vehicle is able to do stationary U-turns. A control system, made up of two decoupled state-space controllers, pilots the motors so as to keep the system in equilibrium.