throttle_sine.py

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#!/usr/bin/env python3
 
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# Copyright (c) 2018, Dataspeed Inc.
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import rospy
import math
 
from std_msgs.msg import Bool
from dbw_fca_msgs.msg import ThrottleCmd
 
 
class SineTest:
    def __init__(self):
        rospy.init_node('sine_test')
        self.pub = rospy.Publisher('/vehicle/throttle_cmd', ThrottleCmd, queue_size=1)
        self.sub = rospy.Subscriber('/vehicle/dbw_enabled', Bool, self.recv_enable)
 
        self.high_peak = rospy.get_param('~high_peak', 0.92)
        self.low_peak = rospy.get_param('~low_peak', 0.08)
        self.period = rospy.get_param('~period', 4)
 
        self.enabled = False
        self.t = 0
        self.sample_time = 0.02
 
        rospy.Timer(rospy.Duration(self.sample_time), self.timer_cb)
 
    def timer_cb(self, event):
        if not self.enabled:
            self.t = 0
            return
 
        amplitude = 0.5 * (self.high_peak - self.low_peak)
        offset = 0.5 * (self.high_peak + self.low_peak)
        cmd = offset - amplitude * math.cos(2 * math.pi / self.period * self.t)
        self.t += self.sample_time
 
        self.pub.publish(ThrottleCmd(enable=True, pedal_cmd_type=ThrottleCmd.CMD_PEDAL, pedal_cmd=cmd))
 
    def recv_enable(self, msg):
        self.enabled = msg.data
 
 
if __name__ == '__main__':
    try:
        node_instance = SineTest()
        rospy.spin()
    except rospy.ROSInterruptException:
        pass