====== Buzz on the Khepera IV ======

The [[https://www.k-team.com/khepera-iv|Khepera IV]] is a commercial robot produced by [[https://www.k-team.com/|K-Team]].

A Buzz port for the Khepera IV is available at https://github.com/MISTLab/BuzzKH4. An ARGoS plugin to simulate the robot is available at https://github.com/ilpincy/argos3-kheperaiv.

===== Supported Devices =====

==== Actuators ====

  * **Wheels**

    * ''set_wheels(lws,rws)'' sets the speed of the wheels to ''lws'' (left wheel speed) and ''rws'' (right wheel speed). The speed is expressed in cm/sec. The maximum speed of the real Khepera is about 20 cm/sec. ''lws,rws'' must be floating point values.

    * ''gotop(ls,as)'' sets the speed of the center of mass of the robot. The speed is expressed as a vector in polar coordinates, where ''ls'' is the linear speed (i.e., the forward speed, in cm/sec) and ''as'' is the angular speed (i.e., in rad/sec). The vector is internally transformed into wheel actuation. ''ls,as'' must be floating point values.

    * ''gotoc(sx,sy)'' sets the speed of the center of mass of the robot. The speed is expressed as a vector in cartesian coordinate, where ''sx'' is the linear speed along the local x axis of the robot (i.e., the forward speed, in cm/sec) and ''sy'' is the linear speed along the local y axis of the robot (a vector pointing left, according to the right-hand rule). The vector is internally transformed into wheel actuation. ''sx,sy'' must be floating point values.

    * To activate this actuator in ARGoS, use the ''differential_drive'' actuator.

  * **LEDs**

    * ''set_leds(r,g,b)'' sets the color of the three LEDs on top of the Khepera IV. The color is expressed with 0-255 integer values for each of the channels (red, green, blue).

    * To activate this actuator in ARGoS, use the ''leds'' actuator.

==== Sensors ====

  * **Proximity sensors**
    * The Khepera IV proximity sensor is a set of 8 infrared emitter/receiver pairs distributed regularly in a ring around the robot. The sensors are numbered 0 to 7. Sensor 0 looks straight ahead, and the numbers increase counterclockwise when looking at the robot from above.
    * ''proximity'' is the Buzz table that contains the proximity readings. Each element of this table (e.g., ''proximity[0]'', ''proximity[1]'', ...) is in turn a table that contains two elements:
      * ''angle'', which corresponds to the angle (expressed in radians) at which the sensor is located on the body of the robot
      * ''value'', which is the actual reading. Each individual sensor is saturated (value ''1.0'') by objects closer than 4 cm; the maximum range of the sensor is 12 cm. Between 4 and 12 cm, the readings follow an exponential law with the distance: ''%%4.14*exp(-33.0*distance)-.085%%''.
      * To activate this sensor in ARGoS, use the ''kheperaiv_proximity'' sensor.

  * **Light sensors**
    * The Khepera IV light sensor is a set of 8 infrared emitter/receiver pairs distributed regularly in a ring around the robot. The sensors are numbered 0 to 7. Sensor 0 looks straight ahead, and the numbers increase counterclockwise when looking at the robot from above.
    * ''light'' is the Buzz table that contains the light readings. Each element of this table (e.g., ''light[0]'', ''light[1]'', ...) is in turn a table that contains two elements:
      * ''angle'', which corresponds to the angle (expressed in radians) at which the sensor is located on the body of the robot
      * ''value'', which is the actual reading. The sensors all return a value
between 0 and 1, where 0 means nothing within range and 1 means the perceived
light saturates the sensor. Values between 0 and 1 depend on the distance of the perceived light. In ARGoS, each reading ''R'' is calculated with ''%%R=(I/x)^2%%'', where ''x'' is the distance between a sensor and the light, and ''I'' is the reference intensity of the perceived light. The reference intensity corresponds to the minimum distance at which the light saturates a sensor.
      * To activate this sensor in ARGoS, use the ''kheperaiv_light'' sensor.

  * **Ultrasound sensors**
    * The Khepera IV ultrasound sensor is a set of 5 emitter/receiver pairs distributed regularly in an arc in front of the robot. The sensors are numbered 0 to 4. Sensor 0 looks straight ahead, and the numbers increase counterclockwise when looking at the robot from above.
    * ''ultrasound'' is the Buzz table that contains the ultrasound readings. Each element of this table (e.g., ''ultrasound[0]'', ''ultrasound[1]'', ...) is in turn a table that contains two elements:
      * ''angle'', which corresponds to the angle (expressed in radians) at which the sensor is located on the body of the robot
      * ''value'', which is the actual distance of the detected obstacle in cm. Each individual sensor is saturated by objects closer than 25 cm; the maximum range of the sensor is 200 cm.
      * To activate this sensor in ARGoS, use the ''kheperaiv_ultrasound'' sensor.

  * **LIDAR sensor**
    * The Khepera IV LIDAR sensor returns 682 readings in a 270 degrees arc (if not configured to return less readings in the ''.argos'' file).
    * ''lidar'' is the Buzz table that contains the LIDAR readings. Each element of this table (e.g., ''lidar[0]'', ''lidar[1]'', ...) is the distance of the object detected by a specific laser beam.
      * To activate this sensor in ARGoS, use the ''kheperaiv_lidar'' sensor.

  * **Battery sensor**
    * This sensor returns the state of the battery.
    * ''battery'' is a table that contains two elements:
      * ''%%available_charge%%'', a value between 0.0 and 1.0
      * ''%%time_left%%'', the number of control steps before battery depletion
      * To activate this sensor in ARGoS, use the ''battery'' sensor.

  * **Positioning sensor** (ARGoS only)
    * This sensor is a sort of GPS, only available in ARGoS. The positioning sensor returns the current pose of the robot.
    * ''pose'' is a table that contains two elements:
      * ''position'', a 3D array ''{x, y, z}''
      * ''orientation'', an array ''{yaw, pitch, roll}''
      * To activate this sensor in ARGoS, use the ''positioning'' sensor.