The Robotics Primer Workbook Developed by  USC, iRobot® and Microsoft® Robotics Studio

Categories: Exercise | Player Exercise | Command Module Exercise

Sensors::Exercise5:Laser Sensor

Setup

Laser sensors are very expensive devices. They also weigh more than the robots can support and have significant power requirements. Therefore, this exercise will rely on simulating the lasers. All that is required to complete this exercise is a standard desktop/laptop computer. The negative aspects of lasers (weight and power) are offset by greater range, accuracy, frequency, and field of view than sonar and IR. The simulated laser we will use is the SICK LMS 200. This laser has a 180 degree field of view, range of 8 meters, and resolution of 1mm.

Part 1:Obstacle Avoidance

An obstacle avoidance routine is a great way to introduce new sensors. Previous exercises have used either a single sonar or infra-red sensor which both have a narrow field of view. With the laser sensor you have access to 180 degrees of range data. This will make obstacle avoidance much easier, and hopefully more accurate.

Your obstacle avoidance routine should move the robot in a straight line and avoid all obstacles. The robot should smoothly change its trajectory before reaching an obstacle.

Part 2:Robot Following

This problem makes use of a special feature of the laser ranger finder. With each range reading an intensity value is also returned. This intensity value can be used to measure the reflectance of an object. Special photoreflective paper can produce a near perfect reflection. This paper can be used as a special marker that is easily detected by a laser.

With multiple robots it is important to know or detect where your teammates are. This can be accomplished by attaching the photoreflective paper to each robot. With this setup each robot can easily detect the members of its team.

This problem involves two simulated robots. One robot has a special marker on it, and the other has a laser range finder. The first robot with the marker will be manually controlled. The second robot must be programmed to follow the first. Your job is to write a controller for the second robot such that it never looses sight of the first.