rm_suspension

Rigid body dynamics simulation for suspension design of RoboMaster robots

Simulation type:

• Drop from 0.5 meter height
• Run down the stairs
• Fly the ramp
• Brake in maximum speed;
• Diagonally across the ramp

Dependencies:

• Eigen
• ROS (for visualization and params loading)

Getting started

Install dependencies

• ROS - http://wiki.ros.org/ROS
• Eigen - http://eigen.tuxfamily.org

NOTE: on Ubuntu 16.04 or 18.04, you may instead install Eigen with

sudo apt-get install libeigen3-dev -y

Download and build code

1. Get the source:

git clone git@github.com:QiayuanLiao/rm_suspension.git

This is a ros_package,you should put it in your ROS workspace.

2. Download the a demo rm_description package and put it to the workspace too. NOTE: the rm_description package is generated by Solidworks and contains a URDF file that describes the meshes, coordinate system and inertia of robot. But we only use it for visualization!!! You can run without rm_description, the whole computing process will still work correctly.

3. Make in your workspace

catkin_make
source devel/setup.bash

Test

Open a new terminal,then type:

roslaunch rm_suspension run_sim.launch

You will get a Rviz interface:

Then,you need to open config by Ctrl+o

You should select sim.rviz in the rm_suspension/config and import it, then you will see

and the terminal will appear options like these,you can choose different simulation scenes according to the hint.

Analysis

1. rqt_plot

   There are two rqt_plot on the right of the interface, you can choose several variables of the robot and dispaly it in curve form. The two most useful variables are spring_length and the base_twist/angular. For example, you can judge whether the spring stroke is exhausted by observing the curve of the spring_length, base_twist/angular could tell you the pose of the robot. You can scale the curve by holding down the right mouse button in rqt_plot.

   

2. Rvis

   On the left of the interface, you can observe the movement of the robot, which plays a significant role in flying the ramp.

Simulate your own robot

Coordinate System

The definition of the coordinate system is shown below. NOTE:

1. The forward direction of chassis is along the +X axis.
2. The X axis of suspension_* should parallel with the X axis of wheel_* .
3. suspe_q_offset(-0.32rad in the demo) contained by the following parameter file should be set casue by the limit of spring length.

Parameter

In rm_suspension/config/sim_param.yaml, there are many robot parameters, you can test different effects on robot performance by changing the numerical value.

NOTE:

1. all parameters about suspensions or wheels are defined by suspension_0 and wheel_0.
2. the Inertia for a rigid body should be computed by Solidworks and is taken about the origin of the frame itself.
3. Every time you change a variable of the robot, you should relaunch.

URDF

Previously mentioned, the URDF(rm_description) only for visualization. Because I can't find how to output the inertia of the rigid body correctly, and I am too lazy to write a URDF parser. You can use the solidworks plugin to export the URDF file of your robot.

rm_suspension 中文版README

这是一个RoboMaster机器人悬挂设计的刚体动力学仿真器

仿真类型：

• 从0.5米高跌落
• 冲下阶梯
• 飞坡
• 最大速度制动
• 斜穿过坡道

依赖:

• Eigen
• ROS (用于可视化和参数加载)

入门

安装依赖

• ROS - http://wiki.ros.org/ROS
• Eigen - http://eigen.tuxfamily.org

注: 在 Ubuntu 16.04 或 18.04上， 你可以通过以下指令安装Eigen

sudo apt-get install libeigen3-dev -y

下载并编译代码

1. 获取源代码：

   git clone git@github.com:QiayuanLiao/rm_suspension.git
   

   这是一个ros_package，你需要把它放入你的ROS工作区。

2. 下载rm_description 包，并将其放到工作区。 注：rm_description由Solidworks生成，包含描述机器人网格、坐标系和惯性的URDF文件。 但我们只把它用于可视化！！！你可以在没有rm_description的情况下运行程序，整个计算过程仍将正常工作。

3. 在你的workspace中执行编译命令

   catkin_make
   source devel/setup.bash
   

测试

打开一个新的终端，然后输入：

roslaunch rm_suspension run_sim.launch

你会看到一个Rviz界面：

然后,你需要通过Ctrl+o 打开配置

选择 rm_suspension/config中的sim.rviz 这个文件并确定

此刻终端会出现以下这些选项，你可以根据提示选择不同的模拟场景

分析

1. rqt_plot

界面右侧有两个rqt_plot的图框，你在选框中可以选择机器人的多个变量，并且将变量数值以曲线形式显示出来。最为有用的两个变量是spring_length和base_twist/angular。例如，你可以通过观察spring_length的变化曲线来判断弹簧行程是否用尽，通过base_twist/angular曲线来观察机器人的姿态变化。在rqt_plot中按住鼠标右键可以缩放曲线。

2. Rvis

在界面左侧，你可以观察到机器人的运动状态，在飞坡的测试过程中起到尤其重要的作用。

模拟你自己的机器人

坐标系

坐标系的定义如下所示。 注:

1. 底盘的前进方向是沿着+X轴。
2. 悬架的X轴应与车轮的X轴平行。
3. 以下参数文件包含的suspe_q_offset（演示中为-0.32rad）应根据弹簧长度的限制进行设置。

参数

在rm_suspension/config/sim_param.yaml中，罗列了机器人的参数，你可以通过改变参数数值来测试其对机器人性能的不同影响。

注:

1. 悬架或车轮的所有参数都由suspension_0和wheel_0定义。
2. 刚体的惯性通过Solidworks计算，并取框架本身的原点。
3. 每次更改机器人的变量时，都应该重新启动启动文件。

URDF

前面提到过，URDF（rm_description）仅用于可视化。 因为我找不到如何正确输出刚体的惯性，而且我懒得编写URDF解析器，你可以使用 solidworks plugin 导出你的机器人的urdf文件。