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urdf文件结构讲解 以四足机器人minitaur为例

人工智能 我是。 1365次浏览 已收录 0个评论 手机上查看
文章索引目录
[隐藏]

.文章目录

 

  • 介绍
  • minitaur urdf解析
    • base_chassis_link
    • chassis right
    • motor
    • upper_leg
    • lower_leg
  • 注意

 

1.1.介绍

  URDF全称为Unified Robot Description Format,中文可以翻译为“统一机器人描述格式”。与计算机文件中的.txt文本格式、.jpg图像格式等类似,URDF是一种基于XML规范、用于描述机器人结构的格式。根据该格式的设计者所言,设计这一格式的目的在于提供一种尽可能通用(as general as possible)的机器人描述规范。URDF创造的机器人模型包含的内容有:  

  • 连杆 link
  • 关节 joint
  • 运动学参数 axis
  • 动力学参数 dynamics
  • 可视化模型 visual
  • 碰撞检测模型 collision

 

1.1.minitaur urdf解析

 

 

<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>link <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>base_chassis_link<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
	<span class="token comment"><!--物理型状--></span>
	<span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>..第一个长方体.<span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
	<span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>..2..<span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
	<span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>..3..<span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
	<span class="token comment"><!-- 设置碰撞--></span>
	<span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span>...<span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
	<span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span>...<span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
	<span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span>...<span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
	<span class="token comment"><!--设置属性例如质量,惯量--></span>
	<span class="token tag"><span class="token punctuation"><</span>inertial<span class="token punctuation">></span></span>...<span class="token tag"><span class="token punctuation"></</span>inertial<span class="token punctuation">></span></span>
<span class="token tag"><span class="token punctuation"></</span>link<span class="token punctuation">>
</span></span>
</code>

  效果如下:  
base  

1.1.1.chassis right

 

<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>link <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>chassis_right<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
	<span class="token comment"><!--motor支架--></span>
    <span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span> .... <span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>.... <span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
    
    <span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span> ....<span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>inertial<span class="token punctuation">></span></span>.... <span class="token tag"><span class="token punctuation"></</span>inertial<span class="token punctuation">></span></span>
  <span class="token tag"><span class="token punctuation"></</span>link<span class="token punctuation">></span></span>
</code>

  要添加一个joint约束位置,不然会报错  

<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>joint <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>chassis_right_center<span class="token punctuation">"</span></span> <span class="token attr-name">type</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>fixed<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>axis <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 0 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>parent <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>base_chassis_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>child <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>chassis_right<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>origin <span class="token attr-name">rpy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>-0.0872665 0 0<span class="token punctuation">"</span></span> <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0 -0.10 0.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>limit <span class="token attr-name">effort</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span> <span class="token attr-name">velocity</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>joint_properties <span class="token attr-name">damping</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">friction</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
  <span class="token tag"><span class="token punctuation"></</span>joint<span class="token punctuation">></span></span>
</code>

 
chassis right   chassis left 同理  
chassis left  

1.1.1.motor

 

<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>link <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>motor_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>geometry<span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>mesh <span class="token attr-name">filename</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>tmotor3.obj<span class="token punctuation">"</span></span> <span class="token attr-name">scale</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1 1 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>geometry<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>material <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>white<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>color <span class="token attr-name">rgba</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1 1 1 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>material<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>geometry<span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>cylinder <span class="token attr-name">length</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.026<span class="token punctuation">"</span></span> <span class="token attr-name">radius</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0434<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>geometry<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>inertial<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>mass <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.25<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"><</span>inertia <span class="token attr-name">ixx</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span> <span class="token attr-name">ixy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">ixz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">iyy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span> <span class="token attr-name">iyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">izz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"></</span>inertial<span class="token punctuation">></span></span>
  <span class="token tag"><span class="token punctuation"></</span>link<span class="token punctuation">></span></span></code> 
<code class="prism language-markup has-numbering">
</code>

 

<joint name="motor_front_rightR_joint" type="continuous">
<axis xyz="0 0 1"/>
    <parent link="chassis_right"/>
    <child link="motor_front_rightR_link"/>
    <origin rpy="1.57075 0 0" xyz="0.21 -0.025 0"/>
    <limit effort="100" velocity="100"/>
    <joint_properties damping="0.0" friction="0.0"/>
  </joint>

  上述为右边电机,其余位置安装同理  
在这里插入图片描述  

1.1.1.upper_leg

 

<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>link <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>upper_leg_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>geometry<span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>box <span class="token attr-name">size</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>.01 0.01 .11<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>geometry<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>material <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>grey<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>color <span class="token attr-name">rgba</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.65 0.65 0.75 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>material<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>geometry<span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>box <span class="token attr-name">size</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>.01 0.01 .11<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>geometry<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>inertial<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>mass <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.05<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"><</span>inertia <span class="token attr-name">ixx</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span> <span class="token attr-name">ixy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">ixz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">iyy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span> <span class="token attr-name">iyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">izz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"></</span>inertial<span class="token punctuation">></span></span>
  <span class="token tag"><span class="token punctuation"></</span>link<span class="token punctuation">>
</span></span>
</code>

  注意对于upper_leg左右关节命名不一样,但其实是同一类型关节,这里涉及到minitaur仿真环境中的一些设置  



<code class="prism language-markup has-numbering">  <span class="token tag"><span class="token punctuation"><</span>joint <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>hip_front_rightR_link<span class="token punctuation">"</span></span> <span class="token attr-name">type</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>fixed<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>axis <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 0 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>parent <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>motor_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>child <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>upper_leg_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>origin <span class="token attr-name">rpy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>-1.57075 0 0<span class="token punctuation">"</span></span> <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0 0.06 -0.015<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>limit <span class="token attr-name">effort</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span> <span class="token attr-name">velocity</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>joint_properties <span class="token attr-name">damping</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">friction</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
  <span class="token tag"><span class="token punctuation"></</span>joint<span class="token punctuation">>
</span></span>
</code>

 



<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>joint <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>motor_front_rightL_link<span class="token punctuation">"</span></span> <span class="token attr-name">type</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>fixed<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>axis <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 0 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>parent <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>motor_front_rightL_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>child <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>upper_leg_front_rightL_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>origin <span class="token attr-name">rpy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>-1.57075 0 0<span class="token punctuation">"</span></span> <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0 0.06 -0.015<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>limit <span class="token attr-name">effort</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span> <span class="token attr-name">velocity</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>joint_properties <span class="token attr-name">damping</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">friction</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
  <span class="token tag"><span class="token punctuation"></</span>joint<span class="token punctuation">>
</span></span>
</code>

1.1.1.

1.1.1.lower_leg

 

<code class="prism language-markup has-numbering"><span class="token tag"><span class="token punctuation"><</span>link <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>lower_leg_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
	<span class="token tag"><span class="token punctuation"><</span>contact<span class="token punctuation">></span></span>
		<span class="token tag"><span class="token punctuation"><</span>stiffness <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>10000<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
		<span class="token tag"><span class="token punctuation"><</span>damping <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>10<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
		<span class="token tag"><span class="token punctuation"><</span>lateral_friction <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
  <span class="token tag"><span class="token punctuation"></</span>contact<span class="token punctuation">></span></span>

    <span class="token tag"><span class="token punctuation"><</span>visual<span class="token punctuation">></span></span>
    	<span class="token tag"><span class="token punctuation"><</span>origin <span class="token attr-name">rpy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0 0 0<span class="token punctuation">"</span></span> <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 0 .1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"><</span>geometry<span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>box <span class="token attr-name">size</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>.01 0.01 .2<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>geometry<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>material <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>grey<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>color <span class="token attr-name">rgba</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.65 0.65 0.75 1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>material<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"></</span>visual<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>collision<span class="token punctuation">></span></span>
    	<span class="token tag"><span class="token punctuation"><</span>origin <span class="token attr-name">rpy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0 0 0<span class="token punctuation">"</span></span> <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 0 .1<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"><</span>geometry<span class="token punctuation">></span></span>
        <span class="token tag"><span class="token punctuation"><</span>box <span class="token attr-name">size</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>.01 0.01 .2<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"></</span>geometry<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"></</span>collision<span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>inertial<span class="token punctuation">></span></span>
      <span class="token tag"><span class="token punctuation"><</span>mass <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.05<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
      <span class="token tag"><span class="token punctuation"><</span>inertia <span class="token attr-name">ixx</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span> <span class="token attr-name">ixy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">ixz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">iyy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span> <span class="token attr-name">iyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">izz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"></</span>inertial<span class="token punctuation">></span></span>
  <span class="token tag"><span class="token punctuation"></</span>link<span class="token punctuation">>
</span></span>
</code>

  lower_leg的关节以knee开头命名,joint类型为revolute的需要加入限制,不加模型会报错  

<code class="prism language-markup has-numbering">  <span class="token tag"><span class="token punctuation"><</span>joint <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>knee_front_rightR_link<span class="token punctuation">"</span></span> <span class="token attr-name">type</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>revolute<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
    <span class="token tag"><span class="token punctuation"><</span>axis <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 1 0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>parent <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>upper_leg_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>child <span class="token attr-name">link</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>lower_leg_front_rightR_link<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>origin <span class="token attr-name">rpy</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0 0 0<span class="token punctuation">"</span></span> <span class="token attr-name">xyz</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0 0.01 .055<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>limit <span class="token attr-name">effort</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span> <span class="token attr-name">velocity</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>100<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
    <span class="token tag"><span class="token punctuation"><</span>joint_properties <span class="token attr-name">damping</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span> <span class="token attr-name">friction</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>0.0<span class="token punctuation">"</span></span><span class="token punctuation">/></span></span>
  <span class="token tag"><span class="token punctuation"></</span>joint<span class="token punctuation">>
</span></span>
</code>

 
leg  

1.1.注意

  link和joint都配置好后大概就是这个四脚朝天的样子了(图一),但是建模其实还没有完成,因为各个关节都是开环的(不是并联机构),简单来说就是这时候的minitaur足端是分离的(图二)   urdf部分的使命已经结束了,并联机构部分我们需要在bullet里面添加约束才能实现,使用createConstraint()  

<code class="prism language-python has-numbering">self<span class="token punctuation">.</span>_pybullet_client<span class="token punctuation">.</span>createConstraint<span class="token punctuation">(</span>
          self<span class="token punctuation">.</span>quadruped<span class="token punctuation">,</span> self<span class="token punctuation">.</span>_joint_name_to_id<span class="token punctuation">[</span><span class="token string">"knee_"</span> <span class="token operator">+</span> leg_position <span class="token operator">+</span> <span class="token string">"R_link"</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
          self<span class="token punctuation">.</span>quadruped<span class="token punctuation">,</span> self<span class="token punctuation">.</span>_joint_name_to_id<span class="token punctuation">[</span><span class="token string">"knee_"</span> <span class="token operator">+</span> leg_position <span class="token operator">+</span> <span class="token string">"L_link"</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
          self<span class="token punctuation">.</span>_pybullet_client<span class="token punctuation">.</span>JOINT_POINT2POINT<span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">,</span> KNEE_CONSTRAINT_POINT_RIGHT<span class="token punctuation">,</span>
          KNEE_CONSTRAINT_POINT_LEFT<span class="token punctuation">)
</span>
</code>

 
在这里插入图片描述  


图一



在这里插入图片描述  


开心洋葱 , 版权所有丨如未注明 , 均为原创丨未经授权请勿修改 , 转载请注明urdf文件结构讲解 以四足机器人minitaur为例
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