{"id":377,"date":"2022-03-18T03:50:39","date_gmt":"2022-03-18T03:50:39","guid":{"rendered":"https:\/\/mrsdprojects.ri.cmu.edu\/2022teami\/?page_id=377"},"modified":"2022-12-13T04:21:47","modified_gmt":"2022-12-13T04:21:47","slug":"control","status":"publish","type":"page","link":"https:\/\/mrsdprojects.ri.cmu.edu\/2022teami\/implementation\/control\/","title":{"rendered":"Control"},"content":{"rendered":"\n

The main function of the control subsystem is to generate the low-level control commands that will be sent to the drive by wire actuators to control the motion of the follower. To make the control task easier, we have divided the subsystem into 2 main controller subsystems: <\/p>\n\n\n\n

a. Pure Pursuit Lateral Controller<\/strong><\/h3>\n\n\n\n

Pure pursuit is a path tracking algorithm. It computes the heading angle which is used to compute the steering angle command that moves the vehicle from its current position to reach some look-ahead point in front of the robot. The linear velocity is assumed constant, hence you can change the linear velocity of the robot at any point. The algorithm then moves the look-ahead point on the path based on the current position of the robot until the last point of the path. You can think of this as the robot constantly chasing a point in front of it. The property LookAheadDistance decides how far the look-ahead point is placed.<\/p>\n\n\n\n

The inputs of the lateral control subsystem are the follower local path from the Planning Subsystem and the follower current pose from the Localization Subsystem. The output is steering commands. The subsystem is shown in Figure 1.<\/p>\n\n\n\n

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Figure 1. Lateral Controller<\/figcaption><\/figure><\/div>\n\n\n\n

Test 1. Waypoint Following on ATV<\/h4>\n\n\n\n

We tested the waypoints following on ATV to test the lateral controller as shown below. The follower was able to follow a prerecorded path.<\/p>\n\n\n\n