WEEk 9

Methodology

Micromouse component parts:

1.  High Torque Bipolar Stepper Motor

High torque Bipolar Hybrid Stepper Motor capable of giving whooping 1.86Kg/cm of stall torque at 1.5Amp current (0.75A per winding) at 1.8 degree stepping angle. It is a most ideal stepper motor for your competition winning micromouse.

Specifications:

• Stall Torque: 1.86Kg/cm at 1.5Amp (0.75A per winding), 6V
• Stepping angle: 1.8 degrees / step
• Compatible Motor Driver: A3982 35V, 2A Stepper Motor Driver for Micromouse
• Compatible Wheel: Micromouse wheel 4mm Shaft
• Shaft: Diameter: 3mm, Length: 16mm
• Dimensions: Length and Width: 42mm, Thickness: 23mm
• Mounting: Four 3mm (M3) bolts 31mm apart on the corners
• Winding type: Bipolar
• Winding Resistance: 11Ohms
• Motor weight: 156gms

2.  LSM303DLHC e-Compass 3 axis Accelerometer and 3 axis Magnetometer Module

The LSM303DLHC is a digital 3 axis accelerometer and 3 axis magnetometer with I2C interface. It has full-scale acceleration range of ±2g to ±16g and full scale magnetic field range of ±1.3 to ±8.1 gauss. All the full scale ranges are user selectable. Module has on board low drop voltage regulator which takes input supply in the range of 3.6V to 6V DC. Board has two mounting holes. All 9 pins of the module are arranged in single line. LSM303DLHC’s I2C serial bus interface supports standard (100 KHz) and fast mode (400 kHz). It is most suitable for tilt compensated compass, quadrotor and robotics application. For LSM303DLHC application interface example available based on LPC2148 ARM7 microcontroller. LSM303DLHC has application example based on LPC2148 ARM7 microcontroller.

3.  L3G4200D 3 Axis Digital Gyroscope with Voltage Regulator

L3G4200D is a 3 Axis ultra stable digital gyroscope. It gives unprecedented stability of zero rate level and very good sensitivity over temperature and time. L3G4200D module features an on board low drop out voltage regulator which takes input supply in the range of 3.6V to 6V DC. Board has two mounting holes. All 9 pins of the module are arranged in single line. This gyroscope can be interfaced with the microcontroller over I2C or SPI interface. The L3G4200D has user selectable full scale of ±250, ±500, ±2000 degrees per second and is capable of measuring rates with a user-selectable bandwidth.

4.  A3982 35V, 2A Stepper Motor Driver for Micromouse

A3982 35V 2A Stepper Motor Driver is the most ideal driver for the Micromouse. It can drive bipolar stepper motor with full and half stepping. It has built-in logic translator which allows you to drive stepper motor by just setting direction, step mode and give clock to drive stepper motor. A3082 motor driver has 4 output LEDs connected at the output. These LEDs prove very useful for quick debugging. It is made from high grade double sided PTH PCB to give added strength to the connectors. A3982 motor driver has presetable chopper based current controller which maintains constant current even when step rate is increased. This improves motor torque at the higher step rate significantly.

Specifications

• Rating: 35V, 2Amp.
• Step type: Full step, Half step
• Control inputs: Step clock, direction, step mode, reset, enable
• Indication: Steepper motor output indication by 4 LEDs
• High grade double sided PTH PCB to give added strength to the connectors
• Chopper based current control for improved torque at high step rates

5.  Ball Caster Wheel Compact

Ball caster wheel is an omni directional wheel. This wheel can be used as neutral wheel for the robot.

Specifications

• Base plate diameter - 27.5mm
• Caster wheel diameter - 13.5mm
• Wheel height - 18mm
• Mounting hole - Three, 120° apart, 3mm or 1/8 inch diameter

6.  IR Transmitter and Receiver pair

This is the IR Transmitter and Receiver pair matched pair used in our IR proximity, White Line or Micromouse sensor. It consists of 5mm 940 nanometer wave length high power IR LED and photodiode having peak sensitivity at 940 nanometer wavelength.

Specifications

• IR TX RX size: 5mm diameter package
• IR LED current rating: 30mA nominal, 600mA pulse loading at 1% duty cycle
• IR LED wavelength: 940nM
• Photodiode peak response wavelength: 940nM

WEEK 8

Literature Review

Existing Design

1.  Egg Torte

            The “Egg Torte” micromouse designed by Kato-san won first place in Japan’s Half Sized Micromouse Competition in 2010. It is constructed on a printed circuit board which houses the microcontroller and can be seen in Figure 1. It runs on lithium batteries and operates using four motors, but only two wheels. It appears that one motor turns each wheel and the second set of motors is used to make the mouse run faster after the first mapping run of the maze.

            In demonstrations the Egg Torte travels at a visibly faster rate in long, straight segments of the maze. This design uses four IR sensors to navigate the maze: two looking forward and two looking out to the sides. The front two sensors look across each other to the opposite sides of the maze. By comparing the intensity of IR returned to either sensor, the mouse can determine whether it is travelling down the center of a path in the maze and whether there is a wall directly in front of it. The other two sensors seem to be looking at the walls to find openings where the maze branches away from the current path.

            On the underside of the mouse, there are two pads supporting the front and rear of the mouse to lower friction and prevent the underside of the circuit board from dragging on the ground. This mouse’s algorithm displays some impressively efficient features, such as moving diagonally through zigzags and rounding out its turns, narrowly missing the wall at the inner edge of a corner.

                                        Figure 1: The Egg Torte Micromouse

                  2.   Min7

            The Min7 is a micromouse design that won the All Japan Micromouse competition in 2011. Its design also uses a circuit board with embedded microcontroller as a chassis, but uses only two motors to power its four wheels. The design again uses a lithium polymer battery and infrared sensors, and Figure 2 shows the visor which is placed over the sensors to reduce noise. Weighing in at only 90 grams and having a 10 x 7.5 cm profile, this mouse can reach speeds of up to 3.5 meters per second, solving a maze at competition in four seconds. This design’s algorithm also employs corner cutting and diagonal movement techniques.

                                             Figure 2: Min7 Micromouse

WEEK 7

Literature Review

Rules and Specifications for the Competition 

Specifications:                 

  The micromouse must be self-contained and not use an energy source employing a combustion process. The length and width is restricted to a square region of 25 cm x 25 cm even if the dimensions change its geometry during a run shall not exceed 25 cm x 25 cm. The height is unrestricted. The micromouse should not jump over, climb, scratch, damage, or destroy the walls.                                

 Maze:                                 

  The maze comprised of 16 x 16 multiples of an 18cm x 18cm unit square. The walls were 5 cm high and 1.2 cm thick. Passageways between the walls were 16.8 cm wide. An exterior wall enclosed the entire maze. The sides of the maze were painted white and the top of the walls red. The floor of the maze was made of wood and finished with non-gloss black paint. The coating on the top and sides of the walls were selected to reflect infrared light and the coating on the floor to absorb it.                                                                      

 Time:                                  

  Each participant in the competition was given a time limit of 15 minutes to have their robot run through the maze. Within this time limit, a micromouse can make as many runs as possible.                                  

 Accuracy:                           

  The micromouse was able to detect and avoid collisions with walls. The robot needed to make 90 degree turns and be able to correct itself with proper alignment. The micromouse is evaluated based on the time taken to go from the starting square until it reaches the finish square (the center of the maze). Once the center is reached initially, the mouse needs to continue to explore the maze until it finds the shortest path. The total time is measured from the time the robot is first activated. The team whose mouse compiles the lowest.