Experimental Setup

  We developed an experimental setup as shown in Fig 1. The interaction experiment between the rat and the robot is performed in the "Open-field". "Open-field" is used in an animal study including the animal psychology.
　 In our "Open-field", "Water Feeder", "Food Feeder", "Rearing Sensor", "Grooming Sensor", "Battery Exchanger" are located as shown.And upper two meter of the bottom, "Fixed Camera" for obtaining whole area image and "Tracking Camera" for obtaining local area image are located .
　 The followings are details of the equipments.

Fig.1 Experimental Setup

Equipments

Fig.2 Food Feeder

 　 The food feeder consists of a microcontroller PIC and a stepping motor. This machine releases a food pellet into a plastic bowl on the field when it receives an instruction sent from the PC.

Fig.3 Water Feeder

 　 The water feeder consists of a microcontroller PIC and a servo motor. This machine extends a mouthpiece connected to a water bottle into the field for three seconds when it receives an instruction sent from the PC. During these seconds only, the rats can obtain water.

Fig.4 Battery Exchanger

 　 The battery exchanger consists of a microcontroller PIC, electromagnets for attracting the batteries, 2-DOFs arm and a charger. This machine automatically exchanges the battery on the robot in the experimental field without human intervention. WM-6 moves to the front of the battery exchanger when the battery on the robot is running low. The PC then sends an instruction to the battery exchanger. After that, the arm attracts the dead battery on the robot via electromagnets and exchanges it for a fully charged battery on the charger.

Fig.5 Tracking Camera

   The tracking camera consists of compact CCD camera with a magnifying lens and the 2-DOFs camera mount. The focal length of a lens is 16[mm], and takes a image of locoregional area in the "Open-field" in detail.
This equipment tracks the rat based on the point of rat derived by fixed camera image and takes a image of whole area in the "Open-field".

Fig.6 Grooming Sensor

   The grooming sensor consists of a square board 200 [mm] on each side, a base and a beam with a strain gage. One end of the beam is placed on the base, and the other end supports the board. Each strain gage is connected to an amplifier and the output of the amplifier is connected to an AD conversion board on the PC. The grooming detecting software module installed in the PC measures the voltage on the AD board and then performs FFT. Thus, this module detects grooming by the power spectrum.

Fig.7 Rearing Sensor

   The rearing sensor consists of photo-interrupters placed on the wall, and they are controlled by two microcontrollers. The photo-interrupters are intercepted by the rat during it is rearing. The microcontrollers then detects rat's rearing and send that to the PC.

Experimental System

   We developed an experimental system as shown in Fig. 8. The equipments can be classified in the following categories;"equipments for stimulus presentation"and "measurement equipments of rat's actions".
　 First, "equipments for stimulus presentation" includes "Food Feeder" "Water Feeder" "Battery Exchanger".These equipments communicate with Control PC using radio communication device named Bluetooth and operate under an command of the Control PC.
　 Secondly, "measurement equipments of rat's actions" includes "Rearing Sensor" , "Grooming Sensor" , "CCD Camera". "Rearing Sensor" and "Grooming Sensor" communicate with Control PC by the same token and transmit measuring result to the Control PC. The CCD Camera image is manipulated by real-time image processor on the Control PC.

Fig.8 Experimental System

Control PC

  Software which automatically controls WM-6 and the experimental setups is installed on the PC. This software consists of some software modules involving image processing module, operation generator module, robot controller module and device controller module. This PC has two Bluetooth communication units which support two-way communication with WM-6 or setups. Therefore, this PC automatically performs the interaction experiments and saves data without human intervention.
　 The control PC has an image processing board, and is capturing the images from the CCD camera. Through the board, the image processing module computes the gravity points of the rat and the robot respectively (Fig. 9).
　 The operation generator module generates the motion of WM-6 and the operation of the experimental setups based on the operational patterns which were programed, according to parameters such as the robot’s position, rat’s position and the states of each lever on the robot and the battery voltage of the robot. The algorithm for accelerating the rat’s learning speed is included in this module. 
　 The robot controller module controls the motion of WM-6 by controlling the directions and the velocities of each motor according to the distance and angle.

Fig.9 Image Processing