Wheel Axis Research Articles

Modeling and Simulation of Mold and Die Grinding

Complex molds and dies often need grinding to achieve the required surface finishes and tolerances. Due to complex part geometry and multiple-axis motion, the wheel–workpiece engagement conditions may vary drastically during grinding, which imposes challenges to choose the appropriate workspeeds. This paper presents a modeling approach to optimize mold and die grinding to reduce cycle time while maintaining process parameters such as grinding force and specific removal rate below critical limits. The wheel–workpiece engagement conditions are calculated for each grinding step by processing the NC program, part and wheel geometries. Grinding forces, power, and temperature are calculated and used as decision variables to optimize workspeed to reduce cycle time. Results for grinding a half bottle shaped mold show that the grinding process parameters vary significantly along the wheel axis at any instant and along the grinding path. The grinding process is far from optimum if a constant workspeed is used. Model-based optimization has been shown to reduce cycle time by 50% while achieving much lower grinding forces and power.

Derivation and Simulation on the Academic Profile of the Mecanum Wheel

Mecanum wheel can provide a Omni-directional movement, so to design the academic profile of the Mecanum Wheel become the first problem to be solved. this paper make a projection of the Mecanum wheel to the set of planes that perpendicular to the wheel axes, Derivate the academic profile of the wheel. Use the data to build the model of the wheels. Then import the model to ADAMS to validate the equation we got. The simulation results indicate they have a good Omni-directional mobile performance.

Controle em três eixos para aquisição de atitude por satélite universitário partindo de condições iniciais desfavoráveis

A concepção de um satélite universitário de baixo custo busca atender as restrições de seu lançamento como carga útil secundária. A configuração girostato foi investigada para avaliar o desempenho do Sistema de Controle de Atitude (SCA) autônomo durante a aquisição de atitude quando o satélite se separa do veículo lançador em uma condição inicial desfavorável. A configuração girostato é controlada em três eixos e busca manter voltada para o Sol a única face com o painel solar. Uma roda de momentum, cujo eixo de rotação é ortogonal àquela face, provê rigidez giroscópica para, em conjunto com três bobinas de torque com núcleo de ar, gerar torques para controle de atitude em três eixos. O SCA inicia sua ação a partir da separação, operando em malha fechada com a estimação da atitude e da velocidade angular do satélite. Essas estimativas são fornecidas por um filtro de Kalman estendido (FKE) que processa medidas vetoriais da direção do Sol e do campo geomagnético oriundas de sensores de Sol e magnetômetro triaxial. Partindo de condições desfavoráveis, os resultados mostraram que o apontamento do satélite demanda cerca de um dia e meio dia para prover erro de apontamento inferior a 10º e menos de dois dias para manter o erro abaixo de 0,1º. Em torno do eixo da roda, ocorre oscilação do satélite em torno da referência, mas dentro de uma margem aceitável. A duração das manobras em relação à capacidade de carga das baterias embarcadas confirmou a viabilidade da configuração girostato. O desempenho e a complexidade dessa configuração foram comparados com a estabilização de corpo rígido com rotação spin visando selecionar configuração apropriada para a missão do satélite.

A method for evaluating the vibrational response of racing bicycles wheels under road roughness excitation

The aim of the work was the development of a method for measuring and comparing the vibrational response of different racing rear wheels to the excitation caused by riding on irregular road surfaces. Four different rear wheels were selected for the study. Vertical accelerations at rear wheel axis and at the seatpost were measured during field tests performed while cruising on different road surfaces at different constant speeds. Frequency analysis of acceleration signals was performed using random signal analysis methods. The results show that the ranking between comfort properties of different wheels varies with the road surface roughness and the cruising speed considered.

1P1-F08 自己復元機構を有する倒立振子型移動ロボットの傾斜角と外力の同時推定(車輪型/クローラ型移動ロボット(3))

In the present study, the development of the tour guide robot that explains the exhibit such as the science pavilions to children is advanced, and the inverted type mobile robot that has the self-righting mechanism as a migratory mechanism is adopted. Disturbance observer which distinguished specific external force added by an inclination and external force which loaded on the circumference of a wheel axis was designed. In this paper, it is verified by simulation and experiment whether the disturbance observer is effective in the estimation of an angle of inclination and external force.

A new ball machining method by centreless grinding using a surface grinder

This paper proposes a novel centreless grinding method for machining ceramic balls using a surface grinder. In this method, a compact unit consisting of an ultrasonic shoe, an ultrasonic regulator, a relay controller, a blade, a stopper and their respective holders is installed on the worktable of a surface grinder to conduct centreless grinding operations. The grinding unit was actually constructed and it was experimentally confirmed that the rotational speeds of the ball around its own two axes, one is parallel to the wheel axis and another parallel to the wheel radius, can be controlled well, respectively, by the elliptic motions occurring on the shoe and regulator end-faces. Then, the grinding experiments validated the proposed technique and revealed that the grinding accuracy is significantly affected by the relay switch 'on' and 'off' times, and the ball cross-section roundness was improved from the initial value of 10.13 μm to the final one of 0.88 μm under the optimal grinding conditions.

203 低重心型平行二輪ビークルの搭乗者を含む重心位置制御システムの構築(トレーニング・制御)

In this paper, structure design and modeling of novel seating-type two wheel vehicle with lower position of gravity center is proposed. The vehicle's gravity center is assigned at the lower position than that of the wheel axis, whose vehicle has the structure of the pendulum. Therefore, it enables the passenger to always keep the stable posture, even if the vehicle is in the power-off or control-off state. Then, the gravity center position's adjustment system is installed inside the vehicle body. Swing of the vehicle body generated by the bias of the passenger's gravity center position is controlled by the proposed seat positioning system. As a result, alignment of pitch angle of the vehicle body is possible by a seat positioning system that has been proposed.

Analysis of Effecting Factors on Surface Finish of Fused Silica Glass Grinding with Inclined Ball-Headed Diamond Wheel

Fused silica glass is widely used on the manufacture of optical apparatus and resonators due to it’s interesting optical and vibration properties. In order to machining the complex structures in the resonators and optical apparatus, grinding process with inclined ball-headed diamond wheel is discussed. Analytical model of the grinding process with inclined ball-headed diamond wheel was built firstly. Afterwards grinding experiments were conducted by varying the feed speed, the rotation speed, the cutting depth and the average grain size of the ball-headed diamond wheel. The machining surfaces were characterized by surface profiler to investigate the effect of the grinding parameters on the surface roughness. The measurement result shows the average grain size of the diamond wheel has important influence on the machining surface and the surface roughness at the groove bottom is better than the groove edge due to the wheel axis tilt angle.

Trajectory estimation of a skid-steering mobile robot propelled by independently driven wheels

SUMMARYThis paper analyses a mobile robot with independently rotating wheels travelling on uneven but smooth ground, including ascending or descending surfaces. We formulate a mathematical expression for the energy cost of the robot's movement. For our analysis, we utilise the principle of virtual work and assume that the robot moves with a fixed arrangement of wheel axes and without using a steering handle. The mathematical model reveals that the coefficient of friction and the payload distribution dominate the wheel behaviour, including slipping and skidding. We minimise the virtual work expression to determine the robot's motion complying with driven wheels. The model also enables us to estimate trajectories for different ground conditions. A hybrid robot, PEOPLER-II, is used to demonstrate the predicted motions, including turns and spins, by following angular velocity control rules. Experimental data verifies that the proposed formulation and minimisation of virtual work are valid techniques for predicting a robot's trajectory. The method described is widely applicable to wheeled robots having independently driven wheels.

A modified pressure wheel for the instrumentation of rotary tabletting machines.

Abstract IN any research into tabletting processes, it is necessary to know the force applied at the punch so that the tabletting pressure may be calculated. Much work has been done using single punch machines having strain gauges bonded to the shank of the punch (Higuchi, Nelson & Busse, 1954; Shotton & Ganderton, 1960). High-speed rotary machines require additional sophistication to enable useful results to be obtained, and there are two methods known. The first is that used by Shotton, Deer & Ganderton (1963). The resistance of strain gauges near the punch tips was used to control the frequency of an oscillator, and the signal was transmitted from the rotary part of the machine to a stationary aerial by radio emission. Thus the difficulty of providing a slip ring connection to the strain gauges was circumvented. However, because the radio transmitter took up space normally occupied by punches, it was difficult to obtain readings from more than one pair of punches, and impossible to obtain readings from all. In the second method (Knoechel, Sperry & others, 1967), strain gauges were placed on the compression screws interposed between the arm holding the movable axis of the pressure wheel and the spring used to adjust the compression force applied. Deflection, measured by the strain gauges, was proportional to the force applied to the punch. Since the gauges were stationary, their output could easily be displayed on a cathode ray oscilloscope, and the pressure to each punch recorded as its head passed under the pressure wheel.

Center of Gravity Compensation for Dynamically-Balanced Two-Wheeled Wheelchair System

Two-wheeled systems have many advantages compared to statically stable systems. This paper describes a control strategy of dynamically-balanced two-wheeled wheelchair system that does not have any front casters. In this system, rider can sit the seat and control the motion of the system by adjusting CoG of his/her body. Unlike other commercial two-wheeled systems, CoG position of the upper body is mainly determined by the position of the user. Thus, there is a possibility that CoG position may not overlap with the wheel axis. In that case, sensor information cannot be used to measure the exact position of the CoG. This paper shows an estimation of method of the unknown CoG position for Two-Wheeled Dynamically-Balanced Wheelchair (TWDBW) is considered. Gravity torque observer with a compliance control is utilized to realize stable compensation according to the variable CoG position. Backstepping based nonlinear control design is applied to regulate and track the CoG motion of the upper body in the TWDBW. The validity of proposed method is verified by simulation and experimental results.

2A2-M05 リンク駆動型球車輪を用いたパーソナルモビリティの開発(特殊移動ロボット)

Mobilities with wheels such as cars or bikes which have been used generally have a constrain of their motion and they cannot move toward wheel axis direction. On the other hand, omni-directional mobilities can move toward all direction and rotate on site. Our group has developed link-driven spherical wheel as omni-directional mechanism and omni-directional mobilities with it. Link-driven spherical wheel is superior to traditional spherical wheel mechanism at driving force but have some problem of omni-directional movement. This paper propose algorithm of omni-directional movement for link-driven spherical wheel and report the development of omni-directional mobilities with the wheels.

Trajectory Tracking Strategies with Singularities Avoidance for Groups of Unicycle-type Robots

AbstractThis paper presents the design and analysis of three trajectory tracking control strategies for groups of unicycle-type robots using the leader-followers scheme. The leader converges asymptotically to a predefined trajectory path while the follower robots achieve a desired formation pattern at same time. The control laws are based on a dynamical extension of the kinematic model of unicycles considering the midpoint of the wheels axis of the robots as output function. When the linear velocity of unicycles is close to zero, a complementary control law is enabled momentarily to avoid singularities. It is demonstrated that in the switched closed-loop system, the orientation angles converge to the same value. Finally, some numerical simulations and real-time experiments show the performance of the control strategies.

Road Dust Emissions from Paved Roads Measured Using Different Mobile Systems

Very few real-world measurements of road dust suspension have been performed to date. This study compares two different techniques (referred to as Sniffer and Emma) to measure road dust emissions. The main differences between the systems are the construction of the inlet, different instruments for recording particulate matter (PM) levels, and different loads on the wheel axes (the weight of Sniffer was much higher than that of Emma). Both systems showed substantial small-scale variations of emission levels along the road, likely depending on-road surface conditions. The variations observed correlated quite well, and the discrepancies are likely a result of variations in dust load on the road surface perpendicular to the driving direction that cause variations in the measurements depending on slightly different paths driven by the two vehicles. Both systems showed a substantial influence on the emission levels depending on the type of tire used. The summer tire showed much lower suspension than the winter tires (one nonstudded and one studded). However, the relative importance of the nonstudded versus studded tire was rather different. For the ratio of studded/nonstudded, Emma shows higher values on all road sections compared with Sniffer. Both techniques showed increased emission levels with increasing vehicle speed. When the speed increased from 50 to 80 km hr-1, the relative concentrations increased by 30–170% depending on the tire type and dust load. However, for road sections that were very dirty, Sniffer showed a much higher relative increase in the emission level with the nonstudded tire. Sniffer’s absolute concentrations were mostly higher than Emma’s. Possible reasons for the differences are discussed in the paper. Both systems can be used for studying relative road dust emissions and for designing air quality management strategies.

Path following of a class of non-holonomic mobile robot with underactuated vehicle body

A new dynamic model for a class of two-wheeled mobile robot (2WMR), whose mass centre locates below its wheel axis, is presented. The dynamic model considered as the motion of an underactuated vehicle body can represent the time-varying horizontal distance of the mass centre with respect to the configuration centre. This model can describe the dynamic behaviours of the robot more accurately. By the computed torque approach, a sliding mode controller based on the adaptive gain to overcome the disturbances of the system is proposed. Integrating with the velocity controller, the whole control system is made up of two closed-loop structures. The control algorithm efficiency is confirmed through simulation in the MATLAB environment.

Inverted pendulum control with allowance for energy dissipation

The behavior of an inverted pendulum hinged on the wheel axis is studied. An algorithm is proposed for solving both the problem of pendulum stabilization in a given position relative to the vertical and the problem of controlling the velocity of the platform on which the pendulum is located under conditions of energy dissipation. Recommendations on choosing control system parameters are given, and the time of transitional processes is estimated.

Maximum Torque and Momentum Envelopes for Reaction Wheel Arrays

Spacecraft reaction wheel maneuvers are limited by the maximum torque and/or angular momentum that the wheels can provide. For an n-wheel configuration, the torque or momentum envelope can be obtained by projecting the n-dimensional hypercube, representing the domain boundary of individual wheel torques or momenta, into three dimensional space via the 3xn matrix of wheel axes. In this paper, the properties of the projected hypercube are discussed, and algorithms are proposed for determining this maximal torque or momentum envelope for general wheel configurations. Practical strategies for distributing a prescribed torque or momentum among the n wheels are presented, with special emphasis on configurations of four, five, and six wheels.

기어 그라인딩 장비 가공조건 최적화에 대한 실험적 연구

To improve the gear noise quality, gear tooth grinding machine are widely used in automotive industry. While using the gear profile grinding machine to improve the gear tooth quality of the transmission, several defects such as chattering, tooth waves that cause the gear noise occasionally happened. But it is very difficult to solve that problem, because there is no one who knows the setting up the optimal grinding condition appropriately. The abnormal manufacturing conditions which make the gear noise make the engineer to spend a lot of time, effort, and money. Due to demands for solving the serious abnormal gear noise happened in the automatic transmission in the mass product stage, the vibration checking process in the worm wheel axis, work rotation and fixed axis of the grinding machine were adapted to find the root causes. As a result, gear profile wave are affected by the work rotation axis's unbalance which is caused by worm wheel feeding speed. And a primary and the secondary grinding feeding speed, cutting oil, work fixed forces are also proved as the important factors. After setting up the grinding condition reported in this paper, it was adapted successfully to the grinding machine to manufacture the new automatic transmissions' gear. The gear noise was dramatically disappeared and the process and the results will offer good guides to the engineers who manufacture the gear with the grinding machine.

Kinematic Features of Wheelchair Propulsion of Elite Chinese National Wheelchair Racers

PURPOSE: This study was to investigate kinematic features of wheelchair propulsion among elite Chinese wheelchair racers during Training Camp of the 2008 Paralympic Games. METHODS: Seven wheelchair racers in Chinese National Paralympic Team (2 females, 5 males, age 25±4.4, body mass 60.3±4.6kg, training year 9.1±2.4) were filmed from the sagittal and front views by a MaxTraq motion analysis system at 60 Hz while they propelled their own racing wheelchairs at maximal speeds on a training roller. Seven reflective markers were placed on the right ear, acromion, lateral epicondyle of humerus, styloid process of Ulna, 3rd metacarpophalangeal joint, wheel axis and pushim. Film data were digitized and smoothed before the joint angles, and angular and linear velocities of the upper extremity were calculated. RESULTS: The results showed the drive phase time (DT), recovery time (RT) and cycle time (CT) were 0.095±0.013, 0.252±0.103 and 0.347±0.114 seconds, respectively. The hand contact angle, release angle and range on the pushrim were 44.2°±2.9, 207.8°±20.2 and 163.6° ±21.8, respectively. The maximal shoulder, elbow and wrist joint angles were 24.1°±25.2, 142.4°±32.2 and 158.7°±14.2, respectively in the drive phase and 66.6° ±27.1, 157.1° ±27.2 and 194.2°±15.3 in the recovery phase. The maximal angular velocities at the shoulder, elbow and wrist joints were 189.5°/s±98.2, 255°/s±165.4 and 573.6°/s±262.4 in the drive phase and 506.3±210.5, 465.6±210.1 and 590.8±273.6°/s in the recovery phase. The pattern recognition demonstrated that the Chinese wheelchair racers used the circular pattern with high upper arm elevation in the recovery phase. CONCLUSION: The Chinese national wheelchair racers had faster CT (0.347s) with comparison to other national wheelchair racers (approximately 0.500s). With the circular stroke pattern, the Chinese wheelchair racers sequentially increased their angular velocities from the shoulder to elbow, then to wrist in the drive phase. The greater upper arm elevation at the end of recovery phase may facilitate the racing speed production in the drive phase.

Spacecraft Attitude Control Using a Double-Gimbal Control Moment Gyro

This paper presents a novel attitude control scheme for a spacecraft. It involves the use of a double-gimbal control moment gyro (CMG), wherein the rotational speed of the momentum wheel is kept constant. Tilting the spin axis of the momentum wheel around either an inner or an outer gimbal axis can generate attitude control torques in one rotational direction. In order to compensate for the absence of control torque in the other rotational direction, a combination of rotations of the inner and outer axes is designed to generate a cyclic motion about the spin axis of the momentum wheel resulting in three-axis attitude control. Analytical and numerical algorithms are developed to compute the control inputs, i.e., the tilt angles of the inner and outer gimbal axes, which are responsible for the desired change in attitude. The effectiveness of the proposed control scheme is verified by numerical simulations.