Embedded Motion Control 2019 Group 3

Group members

Collin Bouwens		1392794
Yves Elmensdorp		1393944
Kevin Jebbink		0817997
Mike Mostard		1387332
Job van der Velde		0855969

Useful information

Robot specs document

S-curve equations

Planning

Week 2	Week 3	Week 4	Week 5	Week 6	Week 7	Week 8
Wed. 1 May: initial meeting: getting to know the requirements of the design document.	Mon. 6 May: design document handed in by 17:00. Responsibility: Collin and Mike.	Wed. 15 May: escape room competition.			Wed. 5 June: final design presentation.	Wed. 12 June: final competition.
	Tue. 7 May: first tests with the robot. Measurement plan and test code is to be made by Kevin and Job.	Tue. 14 May: Implementing and testing the code for the Escape Room Challenge
	Wed. 8 May: meeting: discussing the design document and the initial tests, as well as the software design made by Yves. Presentation of the initial design by Kevin during the lecture.	Wed. 15 May: Developing the software design for the Final Challenge

Design document

PDF version

This document describes the process of making the PICO robot succeed the Escape Room Competition and the Final Competition. The PICO robot is a telepresence robot that is capable of driving around while monitoring its environment. In the Escape Room Competition, the robot is placed somewhere inside a rectangular room with unknown dimensions with one doorway that leads to the finish line. Once the robot crosses the finish line without bumping into walls, the assignment is completed. The Final Competition involves a dynamic hospital-like environment, where the robot is assigned to approach a number of cabinets based on a known map, while avoiding obstacles.

Components

The PICO robot is a modified version of the Jazz robot, which is originally developed by Gostai, now part of Aldebaran. The key components of the robot that are relevant to this project are the drivetrain and the laser rangefinder. The drivetrain is holonomic, as it consists of three omni-wheels that allow the robot to translate in any direction without necessarily rotating. This adds the benefit of scanning the environment in a fixed orientation, while moving in any direction. The software framework allows the forward and sideways velocity to be set, as well as the horizontal angular velocity. The framework also approximates the relative position and angle from the starting position.

The laser rangefinder is a spatial measurement device that is capable of measuring the horizontal distance to any object within a fixed field of view. The software framework measures a finite number of equally distributed angles within the field of view and notifies when new measurement data is available. Using this data, walls and obstacles in the environment of the robot can be detected.

Lastly, the robot is fitted with loudspeakers and a WiFi connection according to the data sheet of the Jazz robot. This can be useful for interfacing during operation, as described in the 'Interfaces' section. Whether the PICO robot actually has these speakers and the WiFi connectivity remains to be determined.

Requirements

Different requirement sets have been made for the Escape Room Competition and the Final Competition. The requirements are based on the course descriptions of the competitions and the personal ambitions of the project members. The final software is finished once all the requirements are met.

The requirements for the Escape Room Competition are as follows:

• The entire software runs on one executable on the robot.
• The robot is to autonomously drive itself out of the escape room.
• The robot may not 'bump' into walls, where 'bumping' is judged by the tutors during the competition.
• The robot may not stand still for more than 30 seconds.
• The robot has five minutes to get out of the escape room.
• The software will communicate when it changes its state, why it changes its state and to what state it changes.

The requirements for the Final Competition are as follows:

• The entire software runs on one executable on the robot.
• The robot is to autonomously drive itself around in the dynamic hospital.
• The robot may not 'bump' into objects, where 'bumping' is judged by the tutors during the competition.
• The robot may not stand still for more than 30 seconds.
• The robot can visit a variable number of cabinets in the hospital.
• The software will communicate when it changes its state, why it changes its state and to what state it changes.
• The robot navigates based on a provided map of the hospital and data obtained by the laser rangefinder and the odometry data.

Functions

A list of functions the robot needs to fulfil has been made. Some of these functions are for both competitions, while some are for either the Escape Room or Final Competition. These functions are:

• In general:
  • Recognising spatial features;
  • Preventing collision;
  • Conditioning the odometry data;
  • Conditioning the rangefinder data;
  • Communicating the state of the software.
• For the Escape Room Competition:
  • Following walls;
  • Detecting the end of the finish corridor.
• For the Final Competition:
  • Moving to points on the map;
  • Calculating current position on the map;
  • Planning the trajectory to a point on the map;
  • Approaching a cabinet based on its location on the map.

The key function in this project is recognising spatial features. The point of this function is to analyse the rangefinder data in order to detect walls, convex or concave corners, dead spots in the field of view, and gaps in the wall that could be a doorway. This plays a key role during the Escape Room Competition in order to detect the corridor with the finish line in it, and therefore has a priority during the realisation of the software. For this function to work reliably, it is essential that the rangefinder data is analysed for noise during the initial tests. If there is a significant amount of noise, the rangefinder data needs to be conditioned before it is fed into the spatial feature recognition function. As a safety measure, it is important to constantly monitor the spatial features in order to prevent collisions with unexpected obstacles.

Lastly, the trajectory planning function plays a major role during the Final Competition, as this determines the route that the robot needs to follow in order to get to a specified cabinet. This function needs to take obstacles into account, in case the preferred route is obstructed. This is possible, as the documentation about the Final Competition show a map in which multiple routes lead to a certain cabinet. One of these routes can be blocked, in which case the robot needs to calculate a different route.

Specifications

The specifications describe important dimensions and limitations of the hardware components of the robot that will be used during the competitions. For each component, the specifications of that components will be given, with a source of where this specification comes from.

The drivetrain of the robot can move the robot in the x and y directions and rotate the robot in the z direction. The maximum speed of the robot is limited to ±0.5 m/s translation and ±1.2 rad/s rotation. These values are from the Embedded Motion Control Wiki page. The centre of rotation of the drivetrain needs to be known in order to predict the translation of the robot after a rotation. This will be determined with a measurement.

The dimensions of the footprint of the robot need to be known in order to move the robot through corridors and doorways without collision. The footprint is 41 cm wide and 35 cm deep, according to the Jazz robot datasheet. A measurement will be made to check these dimensions.

The laser rangefinder will be used to detect and measure the distance to objects in the vicinity of the robot. The measurement distance range of the sensor is from 0.1 m to 10.0 m with a field of view of 229.2°. The range of the sensor is divided into 1000 parts. These values are determined with the PICO simulator and need to be verified with measurements on the real robot.

Interfaces

The interfacing of the robot determines how the project members interact with the robot in order to set it up for the competitions. It also plays a role during operation, in the way that it interacts with the spectators of the competitions. On the development level there is an Ethernet connection available to the robot. This allows a computer to be hooked up to the robot in order to download the latest version of the software using git, by connecting to the Gitlab repository of the project group. This involves using the git pull command, which downloads all the content from the repository, including the executable that contains the robot software.

On the operation level it is important for the robot to communicate the status of the software. This is useful for debugging the software, as well as clarifying the behaviour during the competitions. This can be made possible with the loudspeaker, by recording voice lines that explain what the robot currently senses and what the next step is that it will perform. Not only is this functionally important, but it can also add a human touch to the behaviour of the robot. In case that the PICO robot has been altered to not have loudspeakers, it needs to be determined during testing if the WiFi interface can be utilised in order to print messages in a terminal on a computer that is connected to the robot.

Concept system architecture

Control block

The control block contains actuator control and any output to the robot interface.

Actuator control

The actuators are controlled such that the movement of the robot is fluent. This is achieved via implementing an S-curve for any velocity change. General information on S-curves can be found via the link under Useful Information.

At this moment, separate functions are used for accelerating and decelerating for both linear and rotational motion. The plan is to incorporate all acceleration and deceleration in one function.

Test Plan

The test plan describes the initial tests executed on the Pico robot to determine its functionality. The document also describes the initial setup required to couple the robot to a laptop.

Goal

The goal is to perform the initial setup of the robot and to determine the actual properties of the laser range finder, encoders and drive train. For the laser range finder, these properties consist of the range, angle, sensitivity and amount of noise. The most important property for the encoder is its accuracy.

The most important properties of the drivetrain are its accuracy, and its maximum translational and rotational acceleration for smooth movement.

Simulation results

The range of the laser range finder according to the simulation is 10cm to 10m, the angle is +114.6 to -114.6 degrees as measured from the front of the robot. This angle is measured in 1000 parts, per an amount of time that can be determined by the user.

Execution

Initial setup

The initial setup for connecting with the Pico robot is described on the following wiki page: [[1]]

Laser range finder

Two tests can be executed to determine the range, angle and accuracy of the laser range finder. First of all, the output values from the range finder can be saved in a file and compared to actual measured values. The second option is to program the robot drive backward slowly while facing a wall. The program should stop the robot as soon as it does not register the wall anymore. The same can be done while driving forward to determine the minimum range. To determine the angle the robot can be rotated.

Encoders

The values supplied by the encoders are automatically converted to distance in the x- and y-direction and a rotation a in radians. These can be compared to measured values in order to determine the accuracy.

Drive train

The maximum acceleration of the robot can be determined by finding the amount of time it takes over which the maximum velocity of the robot is achieved in a smooth manner. The maximum translational velocity of the robot is set to 0.5 m/s and the maximum rotational velocity to 1.2 rad/s.

Escape room challenge

Escape room challenge state chart

Hospital Competition

Approach

The general approach to the challange is to create a point map of the map of the hospital. The figure below shows such a point map:

A point is placed on diffrent locations on the map. These locations are: at cabinets, on junction, in front of doorways and in rooms. In the placement of these points, it is important that each point can be approached from a diffrent point in a straight line. The goal of these points is that the robot can navigate from one side of the hospital to the other by driving from point to point. The points that the robot can drive to in a straight line from a point are its neighboring points.

The placement of each point is difined by the distance and direction to its neighboring points and its surrounding spatial features. When the robot is on a point (A) and wants to drive to a diffrent point (B), the robot can use the distance and direction to from A to B to drive to where B approximately is. Then, using the spatial features surrounding point B, the robot can more accuratly determine its location compared to B and drive to B. For the path between points, it can be defined whether this path is through a doorway or hallway, or whether its though a room. This can help in how the robot trajectory should be controlled during the driving from point to point.

State Machine

The figure below shows the state machine for this challenge

Wall finding algorithm

To allow PICO to navigate safely, he must know where he is in the world map and what is around him. PICO is equipped with a LIDAR scanner that scans the environment with the help of laser beams. This data is then processed to be able to determine where all walls and objects are. There are many ways in which you can process the data into useful information. A commonly used algorithm is the split and merge algorithm with the RANSAC algorithm as an extension. These methods are also used within this project. In the case of this design, we do the following processing steps:

1. Filtering measurement data
2. Recognizing and splitting global segments (recognizing multiple walls or objects)
3. Apply the split algorithm per segment
   1. Determine end points of segment
   2. Determine the linear line between these end points (by = ax + c)
   3. For each data point between these end points, determine the distance perpendicular to the line (d = abs(a*x+b*y+c)/sqrt(a^2+b^2))
   4. Compare the point with the longest distance with the distance limit value
      • If our value falls below the limit value then there are no more segments (parts) in the global segment.
      • If the value falls above the limit value, the segment is split at this point and steps 3.1 to 3.4 are performed again for the left and right parts of this point.
4. All segment points found are combined using the RANSAC algorithm.

Below is a visual representation of the split principle. The original image is used from the EMC course of 2017 group 10 [2]:

To be extended!!!!

Meeting notes

Week 2 - 1 May

Notes taken by Mike.

Every following meeting requires concrete goals in order for the process to make sense. An agenda is welcome, though it does not need to be as strict as the ones used in DBL projects. The main goal of this meeting is to get to know the expectations of the design document that needs to be handed in next monday, and which should be presented next wednesday. These and other milestones, as well as intermediate goals, are to be described in a week-based planning in this Wiki.

Design document

The focus of this document lies on the process of making the robot software succeed the escape room competition and the final competition. It requires a functional decomposition of both competitions. The design document should be written out in both the Wiki and a PDF document that is to be handed in on monday the 6th of May. This document is a mere snapshot of the actual design document, which grows and improves over time. That's what this Wiki is for. The rest of this section contains brainstormed ideas for each section of the design document.

Requirements:

• The entire software runs on one executable on the robot;
• The robot is to autonomously drive itself out of the escape room;
• The robot may not 'bump' into walls, where 'bumping' is judged by the tutors during the competition;
• The robot has five minutes to get out of the escape room;
• The robot may not stand still for more than 30 seconds.

Functions:

• Detecting walls;
• Moving;
• Processing the odometry data;
• Following walls;
• Detecting doorways (holes in the wall).

Components:

• The drivetrain;
• The laser rangefinder.

Specifications:

• Dimensions of the footprint of the robot, which is the widest part of the robot;
• Maximum speed: 0.5 m/s translation and 1.2 rad/s rotation.

Interfaces:

• Gitlab connection for pulling the latest software build;
• Ethernet connection to hook the robot up to a notebook to perform the above.

Measurement plan

The first two time slots next tuesday have been reserved for us in order to get to know the robot. Everyone who is able to attend is expected to attend. In order for the time to be used efficiently, code is to be written to perform tests that follows from a measurement plan. This plan involves testing the limits of the laser rangefinder, such as the maximum distance that the laser can detect, as well as the field of view and the noise level of the data.

Software design

The overall thinking process of the robot software needs to be determined in a software design. This involves a state chart diagram that depicts the global functioning of the robot during the escape room competition. This can be tested with code using the simulator of the robot with a map that resembles the escape room layout.

Tasks

Collin and Mike: write the design document and make it available to the group members by saturday.

Kevin and Job: write a test plan with test code for the experiment session next tuesday.

Yves: draft an initial global software design and make a test map of the escape room for the simulation software.

Week 3 - 8 May

Notes taken by Collin.

These are the notes from the group meeting on 8th of May.

Strategy

A change was made to the strategy of the Escape Room Challenge. The new strategy is in two parts, a plan A and a plan B. First the robot will perform plan A. If this strategy fails, plan B will be performed. Plan A is to make the robot perform a laser scan, than rotate the robot 180 degrees and perform another scan. This gives the robot information about the entire room. From this information the software will be able to locate doorway and escape the room. This plan may not work, since the doorway may be too far away from the laser to detect it, or the software may not be able to detect the doorway. Therefore, plan B exists. This strategy is to drive the robot to the a wall of the room. Then the wall will be followed right hand side, until the robot crosses the finish.

Presentation

A Powerpoint presentation was prepared by Kevin for the lecture that afternoon. A few remarks on the presentation were:

• Add the 'Concept system architecture', modyfied to have a larger font.
• Add 'Communicating the state of the software' as a function
• Keep the assignment explanation and explanation of the robot hardware short

Concept system architecture

The concept system architecture was made by Yves. The diagram should be checked on its english, since some sentences are unclear. A few changes were made to the spelling. The content of the contentremained mostly the same.

Measuerment results

The first test with the robot did not go smoothly. Connecting with the robot showed more difficult than expected. When the test program was run, it was discovered that the Laser Sensor contained a lot of noise. A test situation, like the escape room, was made and all the data from the robot was recorded and saved. From this data, a algorithem can be desiged to condition the sensor data. The data can also be used for the Spatial Feature Recognition.

Tasks

The task to be finished for next meeting:

• Spatial Feature Recognition and Monitoring: Mike, Yves
• Laser Range Finder data conditioning: Collin
• Control: Job
• Detailed software design for Escape Room Challenge: Kevin (Deadline: 9/5/2019)

The next robot reservations are:

• Tuesday 14/5/2019, from 10:45
• Thursday 16/5/2019, from 14:30

Next meeting: Wednesday 15/5/2019, 13:30 in Atlas 5.213

Week 4 - 15 May

Notes taken by Collin.

These are the notes from the group meeting on 15th of May.

Escape Room Challenge

The test of the software for the Escape Room Challenge was succesfull. Small changes have been made to the code regarding the currents state of the software being shown on the terminal. Also, the distance between the robot and the wall has been increased and the travel velocity of the robot has been decreased. A state machine has been made and put on the Wiki which describes the software.

Wall detection

A Split and Merge algorithm has been develped in Matlab. It can detect walls and corners. The algorithm needs to be further tested and developed. Futhermore, a algorithm needs to be developed to use the information from the split and merge to find the position of the robot on the map. The current plan is to use a Kalman-filter. This needs to be further developed.

Drive Control

The function to smoothly accelerate and decelerate the robot is not yet finished. Once the function has been swown to work in the simulation, it can be tested on the robot. This will be either Thursday 16th of May or the Tuesday after.

In order to succed in the final challenge, better agreements and stricter deadlines need to ben made and followed by the group.

Tasks

• Yves: Filter double points from 'Merge and split' algoritm.
• Mike: Develop the architecture for the C++ project.
• Job: Code a function for the S-curve acceleration for x ,y direction and z rotation.
• Kevin: Develop Kallman-filter to compare the data from 'Merge and split' with a map.
• Collin: Develop a finite state machine for the final challenge

The next robot reservations are:

• Thursday 16/5/2019, from 14:30

Next meeting: Wednesday 22/5/2019, 13:30 in Atlas 5.213