Embedded Motion Control 2017 Group 3 / Initial Design

This page is a part of the Embedded Motion Control Group 3 of 2017.

Overview

There are 2 main goals for PICO (robot).

1. Corridor competition: To navigate through a corridor and take the first exit (that can be either right or left side of PICO) without colliding with the walls.
2. Maze competition: To solve an unknown maze within given time limit, which has doors to be opened and exit the maze without touching any walls.

The overall Initial design of the project is mentioned in the following section:

1. Requirements
2. Specifications
3. Functions
4. Components
5. Interfaces

Requirements

The following requirements are listed for the robot (PICO) to complete maze successfully:

1. PICO should not touch the walls or any other obstacles in the maze at any time instant.
2. PICO must operate fully autonomous (i.e. without input from the team).
3. PICO should not be idle for more than 3 seconds from the start of program unless it has passed the exit.
4. PICO must be able to detect available space using the Laser Range Finder (LRF) and move to the detected space according to the path finding algorithm (this plans the motion).
5. PICO must be able to find the exit within the provided time (≤ 7 sec for maze and ≤ 5 sec for corridor).
6. PICO must be able to detect the objects (dead ends) that have a high probability of being a door.
7. PICO must be able to open the door in the maze and pass through it.

Functions

The functions are separate modules called supervisors. Each supervisor is unaware of what is there inside the other supervisor and there are communicated only through interfaces. This approach makes software architecture simpler, editing easier and error counts lesser. Supervisors are listed below:

1. Path-finding Supervisor
2. Door Handling Supervisor
3. Wall Detection
4. Motion Supervisor
5. Actuator Supervisor

Path-finding Supervisor

Path-finding supervisor is the brain of PICO. It gives relevant directions of motion throughout PICO's travel.

1-Pledge Algorithm: This algorithm is mainly used in Maze challenge to solve the loop structures inside the maze. When an obstacle like loops are present, PICO continue the wall of obstacle until the sum of turns it took become zero. When the rurn counter sum is equal to zero, Pledge algorithm directs PICO to another path which make it to detach from the loop. The input to this function is the wall information which includes front, left and right side space information. Using the inputs, the algorithm sets a motion goals and then PICO moves to achieve those.

2- Cornering: Cornering concept is introduced mainly for Corridor challenge. If space in right or left side is detected, this function instruct for a turn by changing bool turn_corner to true and wait until the motion supervisor is finished turning

Door Supervisor

1-Ring Bell: Ring the bell if it detect the door possible deadends

2-Standstill: Wait for 5 sec to for the door openingsequence.

Wall / Path Detection

1-Read LRF data: Gets raw data from the LRF sensor

2-Filter LRF data: Reduces noise from raw LRF data and splits it into 3 directions (left, right and front).

3-Transform data: Calculate one distance approximation for the 3 directions.

4-Possiblity checker: Calculate for all directions if movement in that direction is possible, taking a ‘safe’ zone around PICO into account.

Motion Supervisor

1-Position stabilizing: Feedback loop that keep PICO approximately in the center of the corridor by implementing a feedback controller for the distance to the walls on the left and right of the robot.

2-Turn Corner: Make a 90 degree turn either on left or on right

Actuator Supervisor

1-Steady PICO: Keep the front of the PICO aligned to the direction of movement.

2-Omniwheels handeling: Set speed and angle of Omniwheels

Interfaces

The interfaces are defined as the movement/flow of data between the functions that are defined in above section. The different interfaces are described below.

1- Sending information about current state, which is the distance to walls at -90 degrees, 0 degrees and 90 degrees from the center point and whether it has potential from moving forward and turning left or right. <Struct with float values and booleans>.

2- Forward information about potential movement.<Struct of Boolean>.

3- Forward information about wall distances.<Struct of floats>.

4- Turning command, which is either 1 (turning left) or 2(turning right). <integer>.

5- Send information about the possibility of a door.<Boolean>.

6- Confirmation that door handling is finished <Boolean>.

7- Setting the values for actuator.<Struct of floats>

Components

1- Sensors: Laser Range Finder (LRF), Odometry (Wheel Encoder).

2- Holonomic base (omni-wheels): Maximum translational speed of 0.5 m/s , Max angular speed of 1.2 rad/s.

3- Embedded platform Computer with Ubuntu 14.04 on an Intel i7 (other specifications are unknown)

4- Bell: To produce sound from PICO so as to open the door.

Documents

The initial design document File:Emc-design-specification.pdf briefly indicates the approach taken towards the problem of solving the maze by the PICO robot, the algorithm used and the system design.

The slides for the initial design presentation can be found here: File:Group3 2017 Initial design presentation.pdf