MBSim

The motorcycle model is based on the open source mulitbody simulation software MBSim. Please download the software under following link: https://www.mbsim-env.de/builds/run/current/win64-dailyrelease/.

Motorcycle model

In the following some information about the model functionalities are given. More details on the model can be found in the following paper: https://www.mdpi.com/2076-3417/10/19/6826.
An updated version of the model using a tire model directly integrated in MBSim and a more realistic visualization (shown in the video below) is available. This model has different data compared to the version presented below and, therefore, cannot be directly used to reconstruct the results shown in the aforementioned paper. If you are interested in working with the new motorcycle model, please contact: francescopassigato@gmail.com or dwisselmann@t-online.de.

Drift_2.mp4

Switch for Dofs

The parameters with the name beginning in "enable_" allow to decide which Dofs are modelled. Set the parameter to 1 to activate the Dof, to 0 to deactivate it.

Contollers

There are two controllers: one for the longitudinal and one for the lateral dynamics. They are present in the group: Group_Controller. This group is then spilt in lateral and longitudinal controller. The parameters relative to each controller are specified in the parameter list definied within the controller itself.

• Lateral dynamics controller: PD controller which allows the motorcycle to reach a speficied roll angle. The desired roll angle can be given with the parameter Setval_roll_angle. The controller receives the signals of actual roll angle and applies a steer moment.
• Longitudinal dynamics controller: PID controller which allows to perform a acceleration-braking maneuver. It acts with a drive moment on the rear wheel or with a brake moment on both wheels according to the Brake_distribution. The desired speed evolution can be specified with the SignalOperation vx_target. In the present version this parameter is set in order for the motorcycle to reach a desired v_end from the inital v0 speed describing a Cosinus function.

Excitations

The motorcycle stability can be tested with some excitations:

• Torque_steer: applies a cosinus shaped steer moment starting at T_To_start and ending at T_To_exc.
• Fy_Impuls: applies a cosinus shaped lateral force to the frame starting at T_To_start and ending at T_To_exc.
• Road weaves can be simulated by setting the following parameters: h_road_weaves for the height, l_road_weaves for their length and n_road_weavesto specify the number.

Motorcycle parameters

The only motorcycle parameters which can be directly changed in MBSim are steering_damper and caster_angle. The other parameters, including geometry, mass-inertia, tyres and stiffnesses-damping are present in the Excel file in the folder Data. In order to change one ore more parameters please execute the following steps:

• Modify the desired parameters in Excel and save the file.
• Execute the script read_excel. This generates five .xml files, which are read from the model.
• If the model was open, reload it.

Troubleshooting (Windows)

The script read_excel is "ready to use" in Matlab. Alternatively it can be run in the open source "Octave". In this case, the Xerces Java 2 package must be downloaded from https://xerces.apache.org/mirrors.cgi#binary. Then the following lines must be added at the beginning of the script:
pkg load io
javaaddpath ("/path/to/xerces-2_12_1/xercesImpl.jar");
javaaddpath ("/path/to/xerces-2_12_1/xml-apis.jar");
Some errors have been encountered when executing these lines. A possible one is: error: javaMethod: could not find library or dependencies: C:\Program Files\Java\OpenJDK_11.0.2\bin\jvm.dll. In this case the solution was to change the system varible JAVA_HOME so that it points to the folder containing the file jvm.dll.
Another error source could result if Octave is not able to find Java (JRE). In this case please make sure to actually have Java. If the error still remains a solution could be to write the following line after pkg load io:
pkg load windows

FMU

MBSim provides some functionalities to produce a so-called Functional Mock-Up (FMU). This is an interface which allows to export the MBSim model and to run it in other environments. The model can be exported as Co-Simulation or Model-Exchange. In the first case the solver in MBSim is exported together with the model; in the second case the solver must be provided from the environment where the model is run. Further information about FMU can be found in (https://fmi-standard.org/). In order to export the FMU from MBSim the following command must be executed from the matlab command line:
system('path\to\mbsim-env\bin\mbsimCreateFMU.exe --cosim path\to\Motorcycle_FMU.mbsx')
The command --cosim is needed to generate a Co-Simulation. Without it a Model-Exchange is generated.
The file Motorcycle_FMU.mbsx is identical to the standard model, but under links there is the possibiliy to define input and outputs for the FMU. Please add inputs and outpus with ExternSignalSource and ExternSignalSink respectively. When importing the FMU for example in Simulink, the inputs and outpus will appear in the related box. Moreover, a suitable solver for the Co-Simulation is already set in Motorcycle_FMU.mbsx.
In Simulink, a bus object for the input and outputs must be created. For that, please run the simulink model containing the FMU. Simulink will throw an error and suggest to create the bus object with the command fmudialog.createBusType(). After that the bus object can be saved to a .mat file and loaded every time before loading the simulink model.
In the directory FMU an example is present, where the FMU model of the motorcycle accepts steering moment as input and provides the roll angle as output. Please follow the configuration in the "example.slx" simulink model. In particular, a bus creator and selector are needed. In the bus creator please select the option "Output as nonvirtual bus"; this option is already selected in the example. Moreover, in the FMU itself, the name of the input and output bus should be changed, for example in "mbs_in" and "mbs_out" as in the proposed file.

Authors

The multibody model was developed by Francesco Passigato (Chair of Automotive Technology at TU Munich) and Dipl.-Ing. Dirk Wisselmann. A part of the rider model was created by Michael Härtl (Master Degree Student at TU Munich). A great contribution was given by Prof. Martin Förg (University of Landshut), who helped to solve several problems and provided lots of suggestions on how to structure the model istelf.

References

• The model parameters are taken from:
  R. S. Sharp, S. A. Evangelou, and D. J. N. Limebeer,
  "Advances in the modelling of motorcycle dynamics",
  Multibody System Dynamics, vol. 12, no. 3, pp. 251-283, 2004.