The innovative method of modeling and kinematics simulation in RecurDyn are proposed, taking a Mecanum wheel platform(MWP) for omnidirectional wheelchair as research object. In order to study the motion characteristics and mobile performance of the MWP, the virtual prototype simulation model is established in SolidWorks, and virtual prototype simulation is carried out in RecurDyn. The experience of simulation for the MWP in RecurDyn is introduced, and the simulation steps and points for attention are described detailedly. The working states of the mobile system in real environment have been simulated through virtual simulation experiments. Four typical motion models including moving forward, moving laterally, moving laterally in the direction of 45°, and rotation have been simulated in RecurDyn. The simulation results exactly reflect the motion of the MWP. By comparing the simulation results with the theoretical results, there are acceptable errors that are relatively less overall in the simulation results. The simulation results can be used to predict the performance of the platform and evaluate the design rationality, and design quality can be improved according to the exposed problem. This paper can provide reference for the simulation of mobile platform by using RecurDyn.
With the development of computer technology and the expansion requirements of engineering application, virtual prototyping technology (VPT) [
Recursive Dynamic (RecurDyn) [
The Mecanum wheel, a kind of omnidirectional wheel, has got a wider range of applications in the field of mobile robots in recent years [
In order to study the motion characteristics and mobile performance of a MWP for an omnidirectional wheelchair, the virtual prototype simulation model was established using SolidWorks software, and virtual prototype simulation was carried out in RecurDyn, before its physical prototype of MWP is being manufactured. The simulation results have promoted the improvement of the prototype design. In this paper, the experience of simulation for the MWP by RecurDyn is introduced, and the simulation steps and points for attention are described detailedly. In the simulation environment of RecurDyn, the simulation analysis of contact collision problem can be carried out quickly and efficiently. The working state of the mobile system in real environment can be simulated through a variety of virtual simulation experiments. The simulation results can be used to predict the performance of the platform and evaluate the rationality of the design, and design quality can be improved according to the exposed problem.
The 3D modeling function of RecurDyn is relatively weak, so the 3D virtual prototype model for simulating in RecurDyn is usually developed in other CAD software in order to improve the modeling efficiency. SolidWorks, an interactive CAD/CAE/CAM software, is powerful in the function of design and modeling and widely applied in the design field. In this paper, designing, modeling and assembling of the MWP were completed by SolidWorks. Before being imported into RecurDyn, the model should be simplified to reduce the amount of data processing and improve the efficiency of simulation calculation. Some parts, such as bearings, bolts, and electrical components, that have less impact on the simulation can be ignored, and the main subject required for study must be retained.
The MWP in this paper is mainly composed of four parts: main body, two rocker arms, four Mecanum wheels, and differential mechanism, as shown in Figure
3D model of the MWP.
The simplified assembly model can be imported into RecurDyn in Parasolid format. In RecurDyn system, the material and name of the parts and components should be changed, and the Joints between the parts should be defined.
The accuracy of the simulation analysis depends on the accuracy of the above Joints creating. The Joints between the components are created under the premise of confirming the constructional and kinematic relation of the parts. In this simulation model, 103 revolute Joints and 4 spherical Joints are created. 96 of these revolute Joints are between rollers and roller axes of the Mecanum wheel. The 4 spherical Joints are in differential mechanism.
By defining relevant motion functions of the revolute Joints between Mecanum wheels and the rocker arms, the virtual prototype can be enabled to simulate motion according to the predetermined requirements. The STEP functions are used to add motion to system in order to prevent the system simulation abnormity caused by abrupt speed variation in the simulation process. The STEP function, a built-in 3-order polynomial approximation of the step function software, usually used to define a relatively smooth STEP function, is suitable for loading the velocity drive smoothly for the platform.
Although the Joints between the parts of the simulation model have been created and the above settings have been completed, the whole model will penetrate the ground under the action of gravity. In order to simulate the motion of the platform, the Contacts between the rollers of the wheels and the ground need to be added. 96 Contacts are generated at one time by using secondary development tool “ProcessNet” to define the above Contacts. This method of Contacts-generating can save operation time and improve modeling efficiency. When the Joints, the Motions, and the Contacts have been defined, the simulation model of MWP has been set up, as shown in Figure
Simulation model of the MWP.
Contact parameters setting.
The MWP in this paper is a typical four-wheel longitudinal symmetrical layout structure [
Structural schematic diagram of the MWP.
According to the inverse kinematics equation of formula (
A constant angular velocity drive function is added to the revolute pair between each wheel and the rocker arm:
Driving parameters setting of the platform in four typical motion states.
Motion mode |
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Straight-line motion |
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Lateral motion |
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Oblique motion at 45° |
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Original-place rotation |
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In order to better show the motion state of the platform in the simulation process, the trajectory of related Marker Point can be displayed using the Marker Trace command during simulation animation. In the simulation, a Marker is set at the center of the mobile platform. The trajectories of the platform’s center in the above four motion modes are shown in Figures
Trajectory of the MWP in straight-line motion.
Trajectory of the MWP in lateral motion.
Trajectory of the MWP in oblique motion at 45°.
Trajectory of the MWP during the original-place rotation.
Figures
The displacement-time curve of the Marker in vertical direction (
Displacement-time curve in the
The velocity-time curves in
Velocity-time curves in
According to formula (
Comparison between simulation results and theoretical results of the platform motion velocity.
Movement type | Simulation results | Theoretical results | Relative error |
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Rectilinear movement |
438.98 | 439.82 | 0.19% |
Lateral movement |
433.57 | 439.82 | 1.42% |
Oblique movement at 45° | |||
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217.41 | 219.91 | 1.14% |
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217.24 | 219.91 | 1.21% |
Original-place rotation |
0.685 | 0.691 | 0.87% |
In order to study the motion characteristics and mobile performance of a Mecanum wheel platform for an omnidirectional wheelchair, the virtual prototype simulation model is established using SolidWorks, and virtual prototype simulation is carried out based on RecurDyn, before its physical prototype of MWP being manufactured. In this paper, the experience of simulation for the MWP by RecurDyn is introduced, and the simulation steps and points for attention are described detailedly.
The working states of the mobile system in real environment have been simulated through a variety of virtual simulation experiments. Four typical motion modes including moving forward, moving laterally, moving laterally in the direction of 45° with horizontal line, and rotation have been simulated by RecurDyn. The trajectory of the related Marker that is set at the center of the mobile platform has been displayed using the Marker Trace command during simulation animation. The trajectories in the above four motion modes show the motion state of the platform clearly in the simulation process. The displacement-time curve of the Marker set on the MWP in vertical direction (
The simulation results can be used to predict the performance of the platform and evaluate the design rationality, and design quality can be improved according to the exposed problem. On the basis of RecurDyn simulation, the design of Mecanum wheel mobile platform has been further optimized, and the physical prototype of omnidirectional wheelchair was designed and manufactured, as shown in Figure
The photo of physical prototype of omnidirectional wheelchair.
This paper shares the experience of modeling and simulation in RecurDyn. The simulation example of the MWP further verifies the feasibility and scalability of the simulation method involved in this paper. This paper can provide reference for the simulation of mobile platform by using RecurDyn.
The authors declare that they have no conflicts of interest.
This work was financially supported by the National Natural Science Foundation of China (no. 51675518) and the Priority Academic Program Development of Jiangsu Higher Education Institutions.