Mujoco基本情况介绍

基本情况

Mujoco是一个跨平台的机器人建模软件。
官方的介绍是这样的：
MuJoCo is a physics engine that aims to facilitate research and development in robotics, biomechanics, graphics and animation, and other areas where fast and accurate simulation is needed.

不同于webots的1G多的大小，Mujoco windows的程序包只有5.7M,让我差点以为眼花了。

下载地址：https://mujoco.org/

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界面

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运行方式

模型查看

windows/linux直接双击/bin目录下的Simulate打开程序
然后将模型的xml文件拖到界面里面，就可以看到模型了

控制

Mujoco需要通过编写程序来实现控制。
在没有提供控制器的情况下，看起来Mujoco会给你的模型给一个默认的控制程序

控制程序的开发是基于C接口的，比如，一个简单的控制程序例子：

#include //for bool
//#include //for usleep
#include

#include "mujoco.h"
#include "glfw3.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"


char filename[] = "../myproject/projectile/ball.xml";

// MuJoCo data structures
mjModel* m = NULL;                  // MuJoCo model
mjData* d = NULL;                   // MuJoCo data
mjvCamera cam;                      // abstract camera
mjvOption opt;                      // visualization options
mjvScene scn;                       // abstract scene
mjrContext con;                     // custom GPU context

// mouse interaction
bool button_left = false;
bool button_middle = false;
bool button_right =  false;
double lastx = 0;
double lasty = 0;

// holders of one step history of time and position to calculate dertivatives
mjtNum position_history = 0;
mjtNum previous_time = 0;

// controller related variables
float_t ctrl_update_freq = 100;
mjtNum last_update = 0.0;
mjtNum ctrl;

// keyboard callback
void keyboard(GLFWwindow* window, int key, int scancode, int act, int mods)
{
    // backspace: reset simulation
    if( act==GLFW_PRESS && key==GLFW_KEY_BACKSPACE )
    {
        mj_resetData(m, d);
        mj_forward(m, d);
    }
}

// mouse button callback
void mouse_button(GLFWwindow* window, int button, int act, int mods)
{
    // update button state
    button_left =   (glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT)==GLFW_PRESS);
    button_middle = (glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_MIDDLE)==GLFW_PRESS);
    button_right =  (glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT)==GLFW_PRESS);

    // update mouse position
    glfwGetCursorPos(window, &lastx, &lasty);
}


// mouse move callback
void mouse_move(GLFWwindow* window, double xpos, double ypos)
{
    // no buttons down: nothing to do
    if( !button_left && !button_middle && !button_right )
        return;

    // compute mouse displacement, save
    double dx = xpos - lastx;
    double dy = ypos - lasty;
    lastx = xpos;
    lasty = ypos;

    // get current window size
    int width, height;
    glfwGetWindowSize(window, &width, &height);

    // get shift key state
    bool mod_shift = (glfwGetKey(window, GLFW_KEY_LEFT_SHIFT)==GLFW_PRESS ||
                      glfwGetKey(window, GLFW_KEY_RIGHT_SHIFT)==GLFW_PRESS);

    // determine action based on mouse button
    mjtMouse action;
    if( button_right )
        action = mod_shift ? mjMOUSE_MOVE_H : mjMOUSE_MOVE_V;
    else if( button_left )
        action = mod_shift ? mjMOUSE_ROTATE_H : mjMOUSE_ROTATE_V;
    else
        action = mjMOUSE_ZOOM;

    // move camera
    mjv_moveCamera(m, action, dx/height, dy/height, &scn, &cam);
}


// scroll callback
void scroll(GLFWwindow* window, double xoffset, double yoffset)
{
    // emulate vertical mouse motion = 5% of window height
    mjv_moveCamera(m, mjMOUSE_ZOOM, 0, -0.05*yoffset, &scn, &cam);
}


// main function
int main(int argc, const char** argv)
{

    // activate software
    mj_activate("mjkey.txt");


    // load and compile model
    char error[1000] = "Could not load binary model";

    // check command-line arguments
    if( argc<2 )
        m = mj_loadXML(filename, 0, error, 1000);

    else
        if( strlen(argv[1])>4 && !strcmp(argv[1]+strlen(argv[1])-4, ".mjb") )
            m = mj_loadModel(argv[1], 0);
        else
            m = mj_loadXML(argv[1], 0, error, 1000);
    if( !m )
        mju_error_s("Load model error: %s", error);

    // make data
    d = mj_makeData(m);


    // init GLFW
    if( !glfwInit() )
        mju_error("Could not initialize GLFW");

    // create window, make OpenGL context current, request v-sync
    GLFWwindow* window = glfwCreateWindow(1244, 700, "Demo", NULL, NULL);
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1);

    // initialize visualization data structures
    mjv_defaultCamera(&cam);
    mjv_defaultOption(&opt);
    mjv_defaultScene(&scn);
    mjr_defaultContext(&con);
    mjv_makeScene(m, &scn, 2000);                // space for 2000 objects
    mjr_makeContext(m, &con, mjFONTSCALE_150);   // model-specific context

    // install GLFW mouse and keyboard callbacks
    glfwSetKeyCallback(window, keyboard);
    glfwSetCursorPosCallback(window, mouse_move);
    glfwSetMouseButtonCallback(window, mouse_button);
    glfwSetScrollCallback(window, scroll);

    double arr_view[] = {90,-45, 4, 0.000000, 0.000000, 0.000000};
    cam.azimuth = arr_view[0];
    cam.elevation = arr_view[1];
    cam.distance = arr_view[2];
    cam.lookat[0] = arr_view[3];
    cam.lookat[1] = arr_view[4];
    cam.lookat[2] = arr_view[5];

    //m->opt.gravity[2]=-1;
    //qpos is dim nqx1 = 7x1; 3 translations + 4 quaternions
    d->qpos[2]=0.1;
    d->qvel[2]=5;
    d->qvel[0]=2;
    // use the first while condition if you want to simulate for a period.
    while( !glfwWindowShouldClose(window))
    {
        // advance interactive simulation for 1/60 sec
        //  Assuming MuJoCo can simulate faster than real-time, which it usually can,
        //  this loop will finish on time for the next frame to be rendered at 60 fps.
        //  Otherwise add a cpu timer and exit this loop when it is time to render.
        mjtNum simstart = d->time;
        while( d->time - simstart < 1.0/60.0 )
        {
            mj_step(m, d);

            //drag force = -c*v^2*unit_vector(v); v = sqrt(vx^2+vy^2+vz^2)
            // vector (v) = vx i + vy j + vz k
            //unit_vector(v) = vector(v)/v
            //fx = -c*v*vx;
            //fy = -c*v*vy;
            //fz = -c*v*vz;
            double vx, vy, vz;
            vx = d->qvel[0]; vy = d->qvel[1]; vz = d->qvel[2];
            double v;
            v = sqrt(vx*vx+vy*vy+vz*vz);
            double fx, fy, fz;
            double c = 1;
            fx = -c*v*vx;
            fy = -c*v*vy;
            fz = -c*v*vz;
            d->qfrc_applied[0]=fx;
            d->qfrc_applied[1]=fy;
            d->qfrc_applied[2]=fz;
        }

       // get framebuffer viewport
        mjrRect viewport = {0, 0, 0, 0};
        glfwGetFramebufferSize(window, &viewport.width, &viewport.height);

          // update scene and render
        opt.frame = mjFRAME_WORLD;
        cam.lookat[0] = d->qpos[0];
        mjv_updateScene(m, d, &opt, NULL, &cam, mjCAT_ALL, &scn);
        mjr_render(viewport, &scn, &con);
        //printf("{%f, %f, %f, %f, %f, %f};\n",cam.azimuth,cam.elevation, cam.distance,cam.lookat[0],cam.lookat[1],cam.lookat[2]);

        // swap OpenGL buffers (blocking call due to v-sync)
        glfwSwapBuffers(window);

        // process pending GUI events, call GLFW callbacks
        glfwPollEvents();

    }

    // free visualization storage
    mjv_freeScene(&scn);
    mjr_freeContext(&con);

    // free MuJoCo model and data, deactivate
    mj_deleteData(d);
    mj_deleteModel(m);
    mj_deactivate();

    // terminate GLFW (crashes with Linux NVidia drivers)
    #if defined(__APPLE__) || defined(_WIN32)
        glfwTerminate();
    #endif

    return 1;
}

这种形式的控制，很容易就可以跟你的控制系统结合在一起，比如构建一个数据管道，将
系统的数据实时传递到Mujoco里面，它甚至不需要跟你的系统耦合起来。

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建模的支持

有两种方法，一种是xml，另外一种是Mujoco特有的
另外，支持stl导入。
一个用stl来渲染的双足机器人例子：

<mujoco model="darwin v1.31">
   <compiler angle="radian" inertiafromgeom="true" meshdir="meshes/"/>
   <size nconmax="100" njmax="500" nstack="-1"/>
   <default>
      <geom material="MatFrame" margin='0.001' />
      <joint limited='true'  frictionloss="0.2" damping="1.06" armature="0.011" axis="0 0 1" pos="0 0 0"/>
	  <position ctrllimited='true' kp='2.65'/>
   default>
   <asset>
		<mesh file="body_coll.stl"/>
		<mesh file="neck_coll.stl"/>
		<mesh file="head_coll.stl"/>
		<mesh file="shoulder_l_coll.stl"/>
		<mesh file="arm_high_l_coll.stl"/>
		<mesh file="shoulder_r_coll.stl"/>
		<mesh file="arm_high_r_coll.stl"/>
		<mesh file="pelvis_l_coll.stl"/>
		<mesh file="thigh1_l_coll.stl"/>
		<mesh file="thigh2_l_coll.stl"/>
		<mesh file="tibia_l_coll.stl"/>
		<mesh file="ankle1_l_coll.stl"/>
		<mesh file="ankle2_l_coll.stl"/>
		<mesh file="pelvis_r_coll.stl"/>
		<mesh file="thigh1_r_coll.stl"/>
		<mesh file="thigh2_r_coll.stl"/>
		<mesh file="tibia_r_coll.stl"/>
		<mesh file="tibia_naked.stl" scale="0.001 0.001 0.001"/>
		<mesh file="ankle1_r_coll.stl"/>
		<mesh file="ankle2_r_coll.stl"/>
		<mesh file="arm_metal_lowres.stl" scale="0.001 0.001 0.001"/>
		
		<texture type="skybox" builtin="gradient" rgb1="1 1 1" rgb2="0 0 0" width="100" height="100"/>
		<texture name="groundplane" type="2d" builtin="checker" rgb1=".7 .7 .75" 
			rgb2=".9 .9 .95" width="500" height="500" mark="edge" markrgb=".1 .1 .1"/>

		<material name="MatPlastic" specular=".8" shininess=".6" reflectance="0.5" rgba=".4 .41 .4 1"/>
		<material name="MatFrame" specular="1.2" shininess=".1" reflectance="0.5" rgba=".21 .2 .2 1"/>
		<material name="MatGnd" texture="groundplane"  texrepeat="5 5" specular=".5" shininess=".01" reflectance="0.1"/>
   asset>
   
    <contact>       
        <exclude body1="head" body2="torso"/>
		<exclude body1="foot_l" body2="tibia_l"/>
        <exclude body1="foot_r" body2="tibia_r"/>
    contact>
	
	
	<worldbody>
		<light directional="false" cutoff="60" exponent="1" diffuse=".5 .5 .5" specular=".1 .1 .1" pos="0.5 0.1 0.8" dir="-0.5 -0.1 -0.8"/>
		<geom name="ground" pos="0 0 0" size="2 2 1" material="MatGnd" type="plane"/>

      <body name="torso" pos="0 0 0.4">
         <inertial diaginertia="6.53693 6.39822 1.88344" mass="0.975599" pos="-0.003053 -0.038651 -0.019268" quat="-0.00879356 0.867004 0.0524199 0.495458"/>
		 <joint type="free" limited='false'  damping="0" stiffness="0" armature="0"/>
         <geom mesh="body_coll" type="mesh" material="MatPlastic"/>
         <body name="neck" pos="0 0 0.0235" quat="0.707107 0 0 0.707107">
            <inertial diaginertia="0.00482356 0.00482356 0.00482356" mass="0.0243577" pos="0.001424 -0.016567 -0.007128" quat="0.640564 0.00150549 0.00338323 0.767896"/>
            <joint name="head_pan" range="-3.141592 3.141592" type="hinge"/>
            <geom mesh="neck_coll" type="mesh" contype='0' conaffinity='0'/>
            <body name="head" pos="0 0 0.02715" quat="0.5 -0.5 -0.5 0.5">
               <inertial diaginertia="0.158397 0.123969 0.1178" mass="0.158042" pos="6.4e-005 -0.018565 -0.007667" quat="0.504401 0.495706 -0.489128 0.510499"/>
               <joint name="head_tilt" range="-.4363323 .959931089" type="hinge"/>
               <geom mesh="head_coll" type="mesh" material="MatPlastic"/>
            body>
         body>
            <body name="shoulder_l" pos="0 0.06035 0" quat=".5 -.5 -.5 -.5">
               <inertial diaginertia="0.0118742 0.00851644 0.00537304" mass="0.013" pos="-0.0135226 0.0102641 0.00139357" quat="0.89853 0.0814684 0.0409894 0.429332"/>
               <joint name="l_shoulder_pitch" range="-2.61799 2.61799" type="hinge"/>
               <geom mesh="shoulder_l_coll" type="mesh" contype='0' conaffinity='0'/>
               
               <body name="arm_high_l" pos="-0.016 0 0.025" quat="0.5 0.5 0.5 -0.5">
                  <inertial diaginertia="0.122178 0.113353 0.0379938" mass="0.17837715" pos="-0.036239 0.000734 0.00066" quat="0.713991 0.698029 0.0283632 -0.0465622"/>
                  <joint name="l_shoulder_roll" range="-1.308997 2.356194" type="hinge"/>
                  <geom mesh="arm_high_l_coll" type="mesh" material="MatPlastic"/>
                  
                  <body name="arm_low_l" pos="-.06 0 -.016" quat="0 0 0.707107 0.707107">
                     <inertial diaginertia="0.0875091 0.0872503 0.0201335" mass="0.037" pos=".013 -.015 0" quat=".707107 0 0 .315"/>
                     <joint name="l_elbow" range="-1.3 1.57" type="hinge"/>
                     <geom mesh="shoulder_l_coll" pos='.016 -.025 0' euler='-1.57 0 0' type="mesh"/>
                     <geom mesh="arm_metal_lowres" pos='.021 0.0055 -0.081' euler='0 -1.57 0' type="mesh"/>
                  body>
               body>
            body>
            <body name="shoulder_r" pos="0 -0.06035 0" euler='1.57 0 1.57'>
               <inertial diaginertia="0.0118742 0.00851644 0.00537304" mass="0.013" pos="-0.013523 0.010264 0.001394" quat="0.89853 0.0814684 0.0409894 0.429332"/>
               <joint name="r_shoulder_pitch" range="-3.141592 3.141592" type="hinge"/>
               <geom mesh="shoulder_r_coll" type="mesh" contype='0' conaffinity='0'/>
               
               <body name="arm_high_r" pos="-0.017 0 0.02478" quat='.5 -.5 .5 .5' >
                  <inertial diaginertia="0.122178 0.113353 0.0379938" mass="0.168377" pos="-0.036239 0.000734 -0.00066" quat="0.713991 0.698029 0.0283632 -0.0465622"/>
                  <joint name="r_shoulder_roll" range="-2.356194 1.308997" type="hinge"/>
                  <geom mesh="arm_high_r_coll" type="mesh" material="MatPlastic"/>
                  
                  <body name="arm_low_r" pos="-0.06 0 0.016" quat="9.38186e-007 -9.38186e-007 0.707107 0.707107">
                     <inertial diaginertia="0.0875091 0.0872503 0.0201335" mass="0.0592885" pos="0 0 0" quat="0.362962 0.448533 -0.589325 0.565485"/>
                     <joint name="r_elbow" range="-1.57 1.3" type="hinge"/>
                     <geom mesh="shoulder_l_coll" pos='.017 -.0575 0' euler='-1.57 0 0' type="mesh"/>
                     <geom mesh="arm_metal_lowres" pos='.012 -0.027 0.081' euler='0 1.57 0' type="mesh"/>
                  body>
               body>
            body>
         <body name="pelvis_l" pos="-0.005 0.037 -0.09355" quat="0 0.707107 0.707107 0">
            <inertial diaginertia="0.122641 0.11137 0.0411301" mass="0.027069" pos="0 0.00048 0.018437" quat="0.998273 -0.0514899 -0.00396715 0.0279885"/>
            <joint name="l_hip_yaw" range="-.9250245036 2.14675498" type="hinge"/>
            <geom mesh="pelvis_l_coll" type="mesh" contype='0' conaffinity='0'/>
            <body name="thigh1_l" pos="0 0 0.028652" quat="0.707107 0.707107 0 0">
               <inertial diaginertia="0.114985 0.0979692 0.0327798" mass="0.167107" pos="7.9e-005 0.018242 0.013873" quat="0.485806 0.506867 -0.504884 0.502165"/>
               <joint  name="l_hip_roll" range="-1.0297442587 .7853981634" type="hinge"/>
               <geom mesh="thigh1_l_coll" type="mesh"/>
               <body name="thigh2_l" pos="0 0 0" quat="0.5 0.5 -0.5 -0.5">
                  <inertial diaginertia="0.114985 0.0979692 0.0327798" mass="0.119043" pos="-0.062965 -0.000323 0.000692" quat="0.485806 0.506867 -0.504884 0.502165"/>
                  <joint name="l_hip_pitch" range="-.5061454831 1.745329252" type="hinge"/>
                  <geom mesh="thigh2_l_coll" type="mesh" material="MatPlastic"/>

                  <body name="tibia_l" pos="-0.093 0 0">
                     <inertial diaginertia="0.115891 0.0933882 0.043901" mass="0.0703098" pos="-0.053955 0.006548 -0.000592" quat="0.456916 0.538297 -0.548699 0.447654"/>
                     <joint name="l_knee" range="-2.2689280276  .1047197551" type="hinge"/>
                     <geom mesh="tibia_naked" pos='0.145 0 0.037' euler='1.57 0 -1.57' type="mesh"/>

                     <body name="ankle1_l" pos="-0.093 0 0" quat="0 1 0 0">
                        <inertial diaginertia="0.120855 0.109532 0.0411304" mass="0.167108" pos="-0.000214 -0.018536 0.013873" quat="0.997965 0.0519065 0.00385358 -0.0368208"/>
                        <joint name="l_ankle_pitch" range="-1.3962634016 1.2566370614" type="hinge"/>
                        <geom mesh="ankle1_l_coll" type="mesh"/>

                        <body name="foot_l" pos="0 0 0" quat="0.707107 -0.707107 0 0">
                           <inertial diaginertia="0.120855 0.109532 0.0411304" mass="0.0794462" pos="-0.025995 -0.009506 -0.000503" quat="0.997965 0.0519065 0.00385358 -0.0368208"/>
                           <joint name="l_ankle_roll" range="-1.0995574288 .7679448709" type="hinge"/>
                           <geom mesh="ankle2_l_coll" type="mesh" material="MatPlastic" contype='0' conaffinity='0'/>
						   <geom type="box" pos="-.027 -.01 0" size=".007 .032 .052" material="MatPlastic"/>
                        body>
                     body>
                  body>
               body>
            body>
         body>
         <body name="pelvis_r" pos="-0.005 -0.037 -0.09355" quat="0 -0.707107 0.707107 0">
            <inertial diaginertia="0.122641 0.11137 0.0411301" mass="0.027069" pos="0 0.00048 0.018437" quat="0.998273 -0.0514899 -0.00396715 0.0279885"/>
            <joint name="r_hip_yaw" range="-2.14675498 .9250245036" type="hinge"/>
            <geom mesh="pelvis_r_coll" type="mesh" contype='0' conaffinity='0'/>
            
            <body name="thigh1_r" pos="0 0 0.028652" quat="0.707107 -0.707107 0 0">
               <inertial diaginertia="0.114985 0.0979692 0.0327798" mass="0.167107" pos="7.9e-005 -0.018242 0.0138735" quat="0.485806 0.506867 -0.504884 0.502165"/>
               <joint name="r_hip_roll" range="-.7853981634 1.0297442587" type="hinge"/>
               <geom mesh="thigh1_r_coll" type="mesh"/>
               
               <body name="thigh2_r" pos="0 0 0" quat="0.5 0.5 -0.5 -0.5">
                  <inertial diaginertia="0.114985 0.0979692 0.0327798" mass="0.119043" pos="0.062965 -0.000323 0.000692" quat="0.485806 0.506867 -0.504884 0.502165"/>
                  <joint name="r_hip_pitch" range="-1.745329252 .5061454831" type="hinge"/>
                  <geom mesh="thigh2_r_coll" type="mesh" material="MatPlastic"/>
                  
                  <body name="tibia_r" pos="0.093 0 0">
                     <inertial diaginertia="0.115891 0.0933882 0.043901" mass="0.0703098" pos="0.053955 0.006548 -0.000592" quat="0.456916 0.538297 -0.548699 0.447654"/>
                     <joint name="r_knee" range="-.1047197551  2.2689280276" type="hinge"/>
                     <geom mesh="tibia_naked" pos='-0.145 0 -0.037' euler='1.57 0 1.57' type="mesh"/>
                     
                     <body name="ankle1_r" pos="0.093 0 0" quat="0 1 0 0">
                        <inertial diaginertia="0.120855 0.109532 0.0411304" mass="0.167108" pos="-0.000214 -0.018536 -0.013873" quat="0.997965 0.0519065 0.00385358 -0.0368208"/>
                        <joint  name="r_ankle_pitch" range="-1.2566370614 1.3962634016" type="hinge"/>
                        <geom mesh="ankle1_r_coll" type="mesh" />
                        
                        <body name="foot_r" pos="0 0 0" quat="0.707107 -0.707107 0 0">
                           <inertial diaginertia="0.120855 0.109532 0.0411304" mass="0.0794462" pos="0.025995 -0.009506 -0.000503" quat="0.997965 0.0519065 0.00385358 -0.0368208"/>
                           <joint name="r_ankle_roll" range="-.7679448709 1.0995574288" type="hinge"/>
                           <geom mesh="ankle2_r_coll" type="mesh" material="MatPlastic" contype='0' conaffinity='0'/>
						   <geom type="box" pos=".027 -.01 0" size=".007 .032 .052" material="MatPlastic"/>
                        body>
                     body>
                  body>
               body>
            body>
         body>
      body>
   worldbody>
   
   
   <actuator>
		<position name='r_shoulder_pitch' 	joint='r_shoulder_pitch'ctrlrange='-1.5 1.5'  	/>
		<position name='r_shoulder_roll'  	joint='r_shoulder_roll' ctrlrange='-.85 1.3'  	/>
		<position name='r_elbow'          	joint='r_elbow'         ctrlrange='-1.55 1.25'	/>
		<position name='r_hip_yaw'        	joint='r_hip_yaw'       ctrlrange='-1 .9'   	/>
		<position name='r_hip_roll'       	joint='r_hip_roll'      ctrlrange='-.7 .45'   	/>
		<position name='r_hip_pitch'      	joint='r_hip_pitch'     ctrlrange='-1.7 .45'  	/>
		<position name='r_knee'           	joint='r_knee'          ctrlrange='-0.05 2.2' 	/>
		<position name='r_ankle_pitch'    	joint='r_ankle_pitch'   ctrlrange='-1.2 1.35' 	/>
		<position name='r_ankle_roll'     	joint='r_ankle_roll'    ctrlrange='-.7 .95'   	/>
		<position name='l_shoulder_pitch' 	joint='l_shoulder_pitch'ctrlrange='-1.5  1.5' 	/>
		<position name='l_shoulder_roll'  	joint='l_shoulder_roll' ctrlrange='-1.25 .85' 	/>
		<position name='l_elbow'          	joint='l_elbow'         ctrlrange='-1.25 1.55' 	/>
		<position name='l_hip_yaw'        	joint='l_hip_yaw'       ctrlrange='-.9 1'   	/>
		<position name='l_hip_roll'       	joint='l_hip_roll'      ctrlrange='-.45 .7'  	/>
		<position name='l_hip_pitch'      	joint='l_hip_pitch'     ctrlrange='-.45 1.7'  	/>
		<position name='l_knee'           	joint='l_knee'          ctrlrange='-2.2  .05' 	/>
		<position name='l_ankle_pitch'    	joint='l_ankle_pitch'   ctrlrange='-1.35 1.2' 	/>
		<position name='l_ankle_roll'     	joint='l_ankle_roll'    ctrlrange='-.95 .7'   	/>
		<position name='head_pan'    		joint='head_pan'       	ctrlrange='-2 2'      	/>
		<position name='head_tilt'   		joint='head_tilt'      	ctrlrange='-.4 .9'    	/>
	actuator>
	
mujoco>