WM-6(Waseda Mouse No.6)

  We developed a rat-robot, WM-6 (Waseda Mouse No. 6) which can interact with rats. WM-6 is a small mobile robot, and radio controlled by a PC. In addition, WM-6 has two levers to interact with rats. The dimensions and performance of WM-6 almost equal to those of a mature rat.

1.Drive System

  WM-6 has 2 drive wheels and 1 omni-directional ball caster. Due to this mobile mechanism, WM-6 is non-holonomically constrained.

Weight 520 [g]
Size 170 x 85 x 100 [mm]
Max Speed
 1.0 [m/s]
Max Rotational Speed
 6.0 [rad/s]

2.Battery

 WM-6 has a Li-ion battery and operates constantly for a minimum 120 [min]. In addition, using the battery exchanger , it is possible to automatically exchange the battery in the experimental field. Therefore, WM-6 is useful for the long experiments which exceed 120 [min].

3.Control System

  WM-6 has a microcontroller PIC (16F877, microchip) and a Bluetooth communication unit. 
　 The electronic system configuration of WM-6 is shown in Fig. 2. The PIC controls the directions and velocities of the left and right wheels (via DC motors) separately according to instructions sent from the PC through the Bluetooth unit. WM-6 has a dual-bridge motor driver and the DC motors are controlled by PWM. In addition, the PIC measures the battery voltage and states of each lever and sends these data to the PC in real time.

4.Interaction Module; Levers

 WM-6 has two levers to interact with rats. On animal psychology, levers have been used in many experiments using rats, for example "the Skinner Box". Pushing levers is not an innate behavior of rats, meaning it is highly likely that pushing the levers observed in experiments is an intentional behavior. This allow a quantitative evaluation of the interaction.
　 These levers consist of touch sensors which are electrically connected to the PIC, and the PIC sends the logic level of each touch sensor to the PC. It is possible to use this data as a parameter on the operation generator module on the PC (as discribed later).

5.Accelerating the Rat's Learning Speed Algorithm

 In 2002, we succeeded in training rats to push the levers on the robot to obtain food. For animals, learning to perform new behavior which was not equipped by nature is very hard. Therefore, in our previous experiment, an experimenter taught that behavior by pushing the levers and feeding a food pellet in front of the rats, and we then considered those rats might learn the robot functions. This learning process is very interesting. Therefor, we tried to train the rats to that behavior, pushing the levers to obtain food, by the robot autonomously demonstrating. We then developed a new operation generation algorithm that enabled the robot to autonomously demonstrate its functions. We called this algorithm "Accelerating the Rat's Learning Speed Algorithm.
（Accelerating the Rat's Learning Speed Algorithm）

Fig.1 System Configuration of WM-6

Fig.2 Rat and WM-6

WM-8(Waseda Mouse No.8)

 We developed a WM-8 which improved small mobile robot WM-6 that an interaction with the rat was possible. As for WM-8, a pellet feeder is implemented, and a robot can exhibit feeds for a rat.

Weight 585 [g]
Size
 120 x 100 x 100 [mm]
Max Speed
 1.0 [m/s]
Max Rotational Speed
 6.0 [rad/s]

1.Drive System

 Like WM-6, two wheels and, wheel wfich is an independent two-wheel-drive type robot using one ball caster what has a larger path than WM-6, and aimed at improvement in turning characteristics etc.

2.Battery

 WM-8 has a Li-ion battery NP-F770(7.2V /10.8Wh(1,500mAh))for a power supply, and drive of 120[min] is possible in succession.

3.Control System

 WM-8 has a microcontroller PIC (16F877, microchip) and a Bluetooth communication unit. 
The PIC controls the directions and velocities of the left and right wheels (via DC motors) separately according to instructions sent from the PC through the Bluetooth unit. WM-6 has a dual-bridge motor driver and the DC motors are controlled by PWM.

4.Pellet Feeder

 The pellet feeder is mounted on WM-8, and positive reinforcement child(food) can be presented directly from the robot to the rat. As a result, construction of more various experiment systems can be expected.

Fig.3 Pellet feeder

Fig4 WM-8