Caster Wheels Research Articles

Development of Agitators for Seeding Forages Using Air Delivery Systems

Air seeders or air drills traditionally have been used for minimum till and direct seeding of cereal, oilseed, and pulse crops. These seeders use an air delivery system to move the seed from a large grain tank to cultivator furrow openers or boots. Air seeders have all the weight of the cultivator attachment on wheels, whereas the air drill cultivator attachment has the weight distributed to caster wheels on the front and the packer wheels on the back. These units have not been used extensively for forage seeding because of seed bridging problems with some types of grass seed over the metering system entry points in the seed tank. This study designed and evaluated modifications to the agitation and metering systems for seeding forages using 3 different types of Canadian-built air seeders. Meadow brome grass (Bromus riparius Rehmann) was used in the seeding trials because of its extreme susceptibility to bridging. The agitator systems for 3 different types of commercially available air seeders were modified with the ultimate goal to design a configuration that reduced seed bridging and provided uniform seed output. Tests were also conducted with a seed and fertilizer mixture as another method of improving uniformity of seed metering and output. None of the air seeders were able to meter and distribute pure meadow brome seed without the use of a modified agitation system. The Bourgault 3165 air seeder was able to effectively meter and distribute the meadow brome grass seed and fertilizer mixture without the agitator modifications and was able to meter and distribute pure meadow brome grass seed with the addition of the modified agitator. The Flexi-coil 172 air seeders required the addition of a horizontal agitator to effectively meter and distribute the seed and fertilizer mixture, and the Morris 6130 was unable to output the mixture of meadow brome grass seed and fertilizer uniformly despite agitator modifications. Field-scale testing indicated that grass forages could be successfully seeded using a full-size air seeder with these modifications. Las sembradoras de aire o sembradoras en hileras de aire tradicionalmente han sido utilizadas en actividades de mínima labranza o siembra directa de cereales, oleaginosas o cultivos hortícolas. Estas sembradoras usan un sistema de aire para mover la semilla de un depósito grande de granos a los surcadores o las mangueras que depositan la semilla en las hileras. Las sembradoras de aire tienen todo el peso del implemento sobre las ruedas mientras que las sembradoras en hileras de aire tienen el peso distribuido en ruedas que abren la hilera en el frente y en ruedas compactadoras en la parte trasera. Estas unidades no han sido usadas extensivamente para la siembra de forrajes debido a que algunos tipos de semilla de zacates presentan problemas de atascamiento en los puntos de entrada del sistema de medición del tanque de semilla. Este estudio diseño y evaluó modificaciones a los sistemas de medición y agitación para la siembra de forrajes usando tres diferentes tipos de sembradoras de aire Canadienses. En los ensayos de siembra se utilizó el “meadow brome grass” (Bromus riparius Rehmann) debido a su extrema susceptibilidad a atascarse. Los sistemas de agitación para los tres diferentes tipos de las sembradoras de aire comercialmente disponibles fueron modificados con el objetivo de diseñar una configuración que reduzca el atascamiento de la semilla y provea una salida uniforme de esta. Las pruebas también se efectuaron con una mezcla de semilla y fertilizante como otro método de mejorar la uniformidad de la medición de la semilla y su salida. Ninguna de las sembradoras de aire fue capaz de medir y distribuir la semilla pura de “meadow brome grass” sin el uso de un sistema de agitación modificado. La sembradora de aire Bourgault 3165 fue capaz de medir y distribuir efectivamente la mezcla de semilla de “meadow brome grass” y fertilizante sin modificaciones al sistema de agitación y fue capaz de medir y distribuir la semilla pura de “meadow brome grass” con la adición del agitador modificado. Las sembradoras de aire Flexi-coil 172 requirieron de la adición de un agitador horizontal para medir y distribuir efectivamente la mezcla de semilla y fertilizante y la sembradora Morris 6130 fue incapaz de producir una salida uniforme de la mezcla de semilla de “meadow brome grass” y fertilizante, a pesar de las modificaciones del agitador. Las pruebas a nivel de campo indicaron que los zacates forrajeros pueden ser sembrados exitosamente usando una sembradora aire de tamaño completo con estas modificaciones.

Odometry based pose determination and errors measurement for a mobile robot with two steerable drive wheels

A trigonometric method is proposed to calculate the pose (position and orientation) of a mobile robot, possessing a locomotion platform with a unique combination of two steerable and driven wheels and two caster wheels. The model of the locomotion platform is derived to deliver timely and accurate odometer information from measurements of drive wheel revolutions and steering angles. Non-systematic errors, mainly caused by wheel slippage, are detected by a new computation method based on the ratios between the two drive wheels' incremental distances. Real-world experiments validate the proposed model and the algorithm's ability to detect non-systematic errors.

Development of Agitators for Seeding Forages Using Air Delivery Systems

Air seeders or air drills traditionally have been used for minimum till and direct seeding of cereal, oilseed, and pulse crops. These seeders use an air delivery system to move the seed from a large grain tank to cultivator furrow openers or boots. Air seeders have all the weight of the cultivator attachment on wheels, whereas the air drill cultivator attachment has the weight distributed to caster wheels on the front and the packer wheels on the back. These units have not been used extensively for forage seeding because of seed bridging problems with some types of grass seed over the metering system entry points in the seed tank. This study designed and evaluated modifications to the agitation and metering systems for seeding forages using 3 different types of Canadian-built air seeders. Meadow brome grass (Bromus riparius Rehmann) was used in the seeding trials because of its extreme susceptibility to bridging. The agitator systems for 3 different types of commercially available air seeders were modified with the ultimate goal to design a configuration that reduced seed bridging and provided uniform seed output. Tests were also conducted with a seed and fertilizer mixture as another method of improving uniformity of seed metering and output. None of the air seeders were able to meter and distribute pure meadow brome seed without the use of a modified agitation system. The Bourgault 3165 air seeder was able to effectively meter and distribute the meadow brome grass seed and fertilizer mixture without the agitator modifications and was able to meter and distribute pure meadow brome grass seed with the addition of the modified agitator. The Flexi-coil 172 air seeders required the addition of a horizontal agitator to effectively meter and distribute the seed and fertilizer mixture, and the Morris 6130 was unable to output the mixture of meadow brome grass seed and fertilizer uniformly despite agitator modifications. Field-scale testing indicated that grass forages could be successfully seeded using a full- size air seeder with these modifications.

The WalkAbout: A new solution for preventing falls in the elderly and disabled

Wolfe RR, Jordan D, Wolfe ML. The WalkAbout: a new solution for preventing falls in the elderly and disabled. Objective To evaluate the performance of a new walking aid, the WalkAbout, for severely disabled and elderly persons. Design Crossover design. Setting Laboratory and nursing home. Participants Sixty-five patients who could not walk independently. Interventions The top rail of the WalkAbout completely encircles the user and is approximately waist high to provide user stability. The footprint of the base is larger in circumference than the top rail, with the legs angled outward to give the device maximum stability. The caster wheels roll easily along the floor as the user walks. Foot brakes on 2 wheels provide stability for entering and exiting the device by walking through the gate. A safety seat prevents falling but does not impede normal gait. Main outcome measures Distance walked, a questionnaire used to assess function of the WalkAbout, and laboratory tests of safety in preventing falls. Results Seventeen subjects could walk only with the WalkAbout. Ninety-seven percent of subjects who could walk with another assistive device walked further with the WalkAbout. Ninety-five percent of subjects said they felt safe while using the device and 92% reported that the WalkAbout safety seat was comfortable. Conclusions The WalkAbout prevents falls and subjects walked further using the WalkAbout than with any other assistive device tested.

Analysis of Driving Backward in an Electric-Powered Wheelchair

The purpose of this study was to examine the influences of caster orientations and driving speeds on the reverse directional stability of electric-powered wheelchairs. An experiment was set up to record wheelchair trajectories and ground reaction forces/moments for the front caster wheels and rear wheels when a wheelchair initiates reverse motions at six initial caster orientations and three desired driving speeds. A kinematic model as well as a dynamic model were developed to simulate the wheelchair motion and conduct a parametric study of different factors on wheelchair reverse directional stability. The experimental and simulation results show agreement, both of which indicate that different caster orientations at the start of reverse driving introduce disturbances and the faster the intended speed, the less deviation of the wheelchair from its desired heading. The center of gravity (CG) was also found to be a dominant influence on the reverse directional stability of power wheelchairs.

Influence of Wheelchair Front Caster Wheel on Reverse Directional Stability

The purpose of this research was to study directional stability during reversing of rear-wheel drive, electric-powered wheelchairs (EPW) under different initial front caster orientations. Specifically, the weight distribution differences caused by certain initial caster orientations were examined as a possible mechanism for causing directional instability that could lead to accidents. Directional stability was quantified by measuring the drive direction error of the EPW by a motion analysis system. The ground reaction forces were collected to determine the load on the front casters, as well as back-emf data to attain the speed of the motors. The drive direction error was found to be different for various initial caster orientations. Drive direction error was greatest when both casters were oriented 90° to the left or right, and least when both casters were oriented forward. The results show that drive direction error corresponds to the loading difference on the casters. The data indicates that loading differences may cause asymmetric drag on the casters, which in turn causes unbalanced torque load on the motors. This leads to a difference in motor speed and drive direction error.

Modelling and control of the motion of a trolley moving on a plane with a time-dependent inclination

This work deals with the modelling and control of the motion of a trolley moving on a plane with a time-dependent inclination. The trolley is composed from two rear wheels, each of them controlled separately, a connecting frame, and a front caster wheel (see Figure 1).

Transportation with hospital beds

Transporting patients in hospital beds is a common task in acute hospital wards. The aim of the study was to explore the influence of different bed wheel arrangements on the effort and difficulties experienced by personnel when transporting patients. Four test beds were used and tested in four common transport situations. Nineteen registered and enrolled nurses participated in the tests. The perception of effort was rated on Borg's category ratio scale, CR-10 and the perceived level of difficulty on the visual analogue scale. ANOVA and Bonferroni post hoc multiple comparisons were conducted to measure which pairs of beds differed significantly. The results show that the wheel arrangements of the beds have a major influence on the effort and difficulties perceived by the personnel. Standard small diameter castor wheels made the bed easier to manoeuvre in limited spaces, while larger wheels on fixed axles made the beds more comfortable to handle during long distance transportation.

The motion of wheeled robots

The equations of motion of three-wheeled robots with two drive wheels and one passive caster wheel are derived and investigated. The control of longitudinal motion and turns of such a robot is implemented by appropriate control of the independent motors of the drive wheels. The research is carried out under the assumption that the robot is moving on a horizontal plane surface and that the wheels do not slip. A system of two non-linear equations with two controls is obtained for the non-holonomic system considered. The dependence of the phase portrait on the values of the constant controls and parameters of the system, taking into account the asymmetry of the robot, is investigated. The results obtained are not only of theoretical but also of practical interest.

The kinematics for redundantly actuated omnidirectional mobile robots

AbstractOmnidirectional mobile robots have been popularly employed in several application areas. However, the kinematics and singularity analysis for these systems have not been clearly identified, especially for the redundantly actuated case, which is common in current omnidirectional mobile robots. In light of this fact, this article introduces two different kinematic approaches for a typical omnidirectional mobile robot having three caster wheels, and examines singularity configurations of such systems. Then, a singularity‐free load‐distribution scheme for a redundantly actuated three‐wheeled omnidirectional mobile robot is proposed. Through simulation, several advantages of the redundantly actuated mobile robot (singularity avoidance, input‐load saving, and exploiting several subtasks) are presented. © 2002 Wiley Periodicals, Inc.

Mechanism, Control and Design Methodology of the Nonholonomic Quasi-Omnidirectional Vehicle 'ODV9'

The purpose of this paper is to discuss the design of ODV9, a nonholonomic quasi-omnidirectional vehicle to be used as a general platform for mobile robots. Omnidirectional mobility is a desirable property for such a platform because indoor mobile robots are often requested to move in a narrow space. ODV9 has four wheel modules, and each module incorporates one motor, one steering brake, and one conventional wheel equipped with a rubber tire. The use of caster wheels means that ODV9 can be operated with just two motors. Compared with other omnidirectional vehicles, the advantages of ODV9 are not limited to the simplicity of its mechanism. Benefiting from being able to use pneumatic tires, ODV9 is capable of moving on somewhat bumpy road surfaces. The disadvantage of ODV9 is inferiority in its maneuverability. The quasi-omnidirectionality means that an arbitrary x, y and yaw motion cannot be achieved. The disadvantage is, however, compensated by proper use of many possible running modes according to the situation. Experimental results and simulations verify the effectiveness of the design. The ability of ODV9 to get over a step and change its width is also discussed.

Mechanism, Control and Design Methodology of the Nonholonomic Quasi-Omnidirectional Vehicle “ODV9”

The purpose of this paper is to discuss the design of ODV9, a nonholonomic quasi-omnidirectional vehicle to be used as a general platform for mobile robots. Omnidirectional mobility is a desirable property for such a platform because indoor mobile robots are often requested to move in a narrow space. ODV9 has four wheel modules, and each module incorporates one motor, one steering brake, and one conventional wheel equipped with a rubber tire. The use of caster wheels means that ODV9 can be operated with just two motors. Compared with other omnidirectional vehicles, the advantages of ODV9 are not limited to the simplicity of its mechanism. Benefiting from being able to use pneumatic tires, ODV9 is capable of moving on somewhat bumpy road surfaces. The disadvantage of ODV9 is inferiority in its maneuverability. The quasi-omnidirectionality means that an arbitrary x, y and yaw motion cannot be achieved. The disadvantage is, however, compensated by proper use of many possible running modes according to the situation. Experimental results and simulations verify the effectiveness of the design. The ability of ODV9 to get over a step and change its width is also discussed.

9C11 キャスタと後輪を考慮した手動車いすの動特性

9C11 キャスタと後輪を考慮した手動車いすの動特性

Design of an Omnidirectional Mobile Robot with 3 Caster Wheels

In this paper, design of a 3-degree-of-freedom mobile robot with three caster wheels is performed. Initially, kinematic modeling and singularity analysis of the mobile robot is performed. It is found that the singularity can be avoided when the robot has more than two wheels on which two active joints are located. Optimal kinematic parameters of mobile robots with three active joint variables and with four active joint variables are obtained and compared with respect to kinematic isotropic index of the Jacobian matrix of the mobile robot which is functions of the wheel radius and the length of steering link.

ARVAND - A SOCCER PLAYER ROBOT

ARVAND is a robot specially designed and constructed for playing soccer in the medium-size league according to RoboCup rules and regulations. This robot consists of a moving mechanism, motion-control hardware, software, and a wireless communication system. The motion mechanism consists of a drive unit, a steer unit, and a castor wheel. Motion control is carried out by a special control board that uses two microcontrollers to carry out the software system decisions and transfers them to the robot mechanics. The software system performs real-time object recognition at the rate of 16 frames a second. Playing algorithms are based on deterministic methods and communication among robots. We have constructed four such robots and successfully proved their performance at RoboCup-99.

Modelling and control of the motion of a trolley: Effect of motor dynamics on the dynamical model

This work deals with the modelling and control of the motion of a trolley. The trolley is composed from two rear wheels, each of them controlled separately by a DC-motor, and from a front castor wheel (see Figure 1). In order to obtain a set of dynamic equations of the trolley motion that include the motor dynamics, the trolley dynamics and the motor dynamics are coupled to obtain a set of third-order differential equations. Then two inverse dynamics transformations are applied successively, to enable one to use linear control for the design of guidance laws for steering the trolley.

Underwater inspection robot—AIRIS 21 ®

Highly reliable, cost-effective and extended examination coverage are three big demands for newly developed ISI equipment. AIRIS 21 (Advanced Inspection System for Reactor Pressure Vessel and Internals) which is a state-of-the-art next generation device, has been developed to reply to these demands. The device can reduce the inspection cost and increase the reliability and inspection coverage. The AIRIS 21 swims in the water toward an area to be inspected and sticks to the vessel wall using two propellers. After it sticks on the wall, the spinning speed of propellers is controlled to keep the device on the wall with constant vacuum force. Then it travels on the wall freely by two driving wheels and one caster wheel. This manner of new examination system is quite different from the other conventional BWR-ID systems. This new inspection system is dramatically reduced its size [W550×L600×H55 (mm)] and weight [13.6 (kg)] compared with conventional system, and also saves ISI from being a critical path work because it needs no special tools, such as a large crane for handling. With AIRIS 21, it is possible to perform ID inspection of RPV welds in parallel with fuel shuffling and other core activities.

Navigation and control of a system composed of a trolley and a mounted two-link manipulator

This work deals with the guidance and control of the motion of a system which is composed of a trolley and a mounted two-link manipulator. The trolley is composed from two rear wheels, each of them controlled separately, and from two front castor wheels (see Figure 1). Denote by ( x, y) the trolley's center of mass, and by α 1 and α 2 the angles with respect to the horizon of the manipulator arms. Given N points P i , i = 1, …, N in the horizontal plane, 2 N angles α kj , k = 1, 2, j = 1, …, N, a finite time interval [0, t f ], and a sequence of times τ 1 = 0 < τ 2 < … < τ N = t f . Based on a dynamical model of the system, and by using the concept of path controllability, a control law for the trolley's rear wheels and for the two-link manipulator torques is derived, to steer the system such that [( x, y), α 1, α 2] will pass through [ P j , α 1 j , α 2 j ] at the time τ j , j = 1, …, N, respectively.

Velocity control of wheeled mobile robots using computed torque control and its performance for a differentially driven robot

This article presents the development of a Computed Torque Control (CTC) scheme for Cartesian velocity control of Wheeled Mobile Robots (WMRs). The literature presents extensive study on the need and suitability of the CTC scheme for robot arms. Many researchers have identified the benefits of using a CTC scheme for mobile robots. There is however very little information on CTC schemes for controlling mobile robots. The need for the CTC scheme stems from the fact that mobile robots (industrial AGVs) employing conventional velocity control schemes experience side slip due to suspended loads while negotiating curves, and the controller gains and accelerations need to be modified for changes in the dynamics. The structure of the proposed control scheme can be employed to control any mobile robot for which an inverse dynamic model exists, as a CTC scheme requires an inverse dynamic model to compute unique values for the motor current for a given trajectory. It is demonstrated that the existence of the inverse dynamic model is guaranteed for all differentially driven WMRs for all operating conditions, and is not affected by the number of castor wheels in the WMR. In the proposed CTC scheme, the linear and angular velocities of the WMR are controlled by adjusting the WMR accelerations, which are computed based on the motor torques required to follow a given trajectory. The motor torque is pre-computed based on a dynamic model of the mobile robotic system. The simulation and experimental results presented for a differentially driven WMR demonstrate that a computed-torque control scheme provides adaptive cruising and steering control for nominally tuned controller gains compared to a conventional velocity controller to achieve proper road following in the presence of changes in the dynamics. © 1997 John Wiley & Sons, Inc.

Sound reflecting shell tower and transporter structure and methods of erecting and storing the towers

An orchestra shell tower and tower transporter system has a plurality of shell towers comprising an acoustic central panel hingedly connected along its side edges to acoustic wing panels. A generally horizontally rearwardly extending tripod-shaped open base is fixed to the lower end of the central panel and counterweights both the central panel and the wing panels. Vertically adjustable dependent legs with stage engaging members are provided on the tower. A tower transporter has a forwardly extending tripod-shaped open base supported on caster wheels and configured to be received within the base of each of the shell towers. Vertically movable lifters on the transporter base have receptors for engaging the legs of each of the tower shells in lifting relationship and actuatable motors are provided on the transporter for raising and lowering the lifters, and thereby the tower engaged by the transporter for supporting the tower in a raised position for travel. The wing panels are fully folded after the shell tower reaches a position for storage and, as the successive towers are brought to the storage position, they are successively nested one with the other. Locking mechanism holds the tower wing panels in folded positions and in the user positions in which they substantially facially align with the central panel.