最近通过学习读取编码器值从而计算出角度，不可避免的了解到了一些TF转换的知识。
接下来将有一个小脚本来看现象（这个脚本是根据校正底盘角度写的）：
#!/usr/bin/env python #coding=utf-8 import rospy from geometry_msgs.msg import Quaternion from nav_msgs.msg import Odometry import tf from math import radians import PyKDL def quat_to_angle(quat): rot = PyKDL.Rotation.Quaternion(quat.x,quat.y,quat.z,quat.w) return rot.GetRPY()[2] class MyOdomRead(): def __init__(self): rospy.init_node('calibrate_angular',anonymous=False) rospy.on_shutdown(self.shutdown) self.testangle = rospy.get_param('~test_angle',360.0) self.test_angle = radians(self.testangle)#这里其实并没有用，但是这里有一个由角度转换为弧度的函数很有意义 self.start_test = rospy.get_param('~start_test',True) self.base_frame = rospy.get_param('~base_frame','/base_footprint') self.odom_frame = rospy.get_param('~odom_frame','/odom') self.tf_listener = tf.TransformListener() rospy.sleep(2) self.tf_listener.waitForTransform(self.odom_frame,self.base_frame,rospy.Time(),rospy.Duration(60.0)) #官方解释：tf provides a nice tool that will wait until a transform becomes available. #翻译：TF提供了一个很好的工具，可以等到转换变得可用为止。 while not rospy.is_shutdown(): self.odom_angle = self.get_odom_angle()#获取角度值--弧度 print self.odom_angle def get_odom_angle(self): try: (trans,rot)=self.tf_listener.lookupTransform(self.odom_frame,self.base_frame,rospy.Time(0)) #官方解释： Until now we used the lookupTransform() function to get access to the latest available transforms in that tf tree, without knowing at what time that transform was recorded. #翻译：我们可以利用lookupTransform()访问该TF树中的最新可用转换，无需知道时间 except (tf.Exception,tf.ConnectivityException,tf.LookupExceptiom): rospy.loginfo("TF转换有问题") return return quat_to_angle(Quaternion(*rot)) def shutdown(self): rospy.loginfo("读取停止中...") rospy.sleep(1) if __name__=='__main__': try: MyOdomRead() except: rospy.loginfo("Calibration terminated")首先运行上面的脚本，然后再运行一个小脚本来使底盘原地沿着z轴转：
#! /usr/bin/env python #coding=utf-8 import rospy from geometry_msgs.msg import Twist class SpeedPub(): def __init__(self): rospy.init_node('speedpub',anonymous=False) self.pub=rospy.Publisher('/cmd_vel',Twist,queue_size=10) rospy.on_shutdown(self.shutdown) self.twister=Twist() while not rospy.is_shutdown(): self.twister.linear.x=0 self.twister.linear.y=0 self.twister.linear.z=0 self.twister.angular.x=0 self.twister.angular.y=0 self.twister.angular.z=0.2 self.pub.publish(self.twister) def shutdown(self): self.pub.publish(Twist()) rospy.loginfo("机器人正在停止，请稍候...") rospy.sleep(4) if __name__=='__main__': try: SpeedPub() except: rospy.loginfo("出错，退出中...")接下来你会如下看到效果
