Update: Weekend Work

Summary: The robot is on its way to being complete. It should be functional by tomorrow night.


Before the presentation we need to:

• Glue in the stepper motors
• Finish the gearbox
• Finish the shell
• Finalize code
• Make a poster? (I have a Trifold if we want it)

Full Group Meeting (11/24)- Lift Gears, Gearbox, and Body Assembly

 Summary: We designed the gears for the lifting mechanism, assembled the gearbox, and started cutting out a neater body.

We started work on our new slimmer body and planned out the interior layout. We also dry fit the gear box with a 114.7:1 ratio (still need to add in the longer axles), and updated our Solidworks models with the rest of the gears for the lifting mechanism.

 

Since the new body was underway, we decided to do strength testing for the original structure; coreboard and cardboard should hold up fine.

As we are wrapping up for the presentation in a little over a week, the remaining tasks are:

• Submit the gears for laser cutting, and attach gears to a shaft
• Purchase axles for both the gearbox and the lifting mechanism
• Wire battery packs and arduino board
• Assemble body and add holes to the sidewalls
• Build/attach a cup holder
• Finalize code

Update: Stair Climbing Code

Summary: Code for climbing up the stairs.

***********************************

#include <Wire.h>

#include <Adafruit_MotorShield.h>

#include "utility/Adafruit_PWMServoDriver.h"

Adafruit_MotorShield AFMSb(0x61);

Adafruit_MotorShield AFMSt(0x60);

//Motors on bottom board:

// Stepper Motor on M1 and M2

Adafruit_StepperMotor *BMotor = AFMSb.getStepper(200, 1);

// Stepper Motor on M3 and M4

Adafruit_StepperMotor *FMotor = AFMSb.getStepper(200, 2);

//Motors on top board:

//DC Motor on M1

Adafruit_DCMotor *LMotor = AFMSt.getMotor(1);

//DC Motor on M2

Adafruit_DCMotor *RMotor = AFMSt.getMotor(2);

//Sets lift motor directions

int up = FORWARD;

int down = BACKWARD;

//Sets motor speeds

int liftSpeed = 50;

int moveSpeed = 50;

int count = 0;

Update: New Mounting Bracket

Summary: Resolved bracket issues and resized platform.


Brendan and I talked about modifying the 3D printed mounting bracket, and we decided that it would not be necessary. The erector set has four of these bracket pieces, that should suffice.

Additionally, if we cut down the platform so that the edge is .5 in from the rack holes, then we will reduce our axle size, and can used what we already have. This means we don't need to print those either. Then we can buy two hex axles for the lifting mechanism, to resolve the issue of the plastic not being strong enough.

Update: Lift Team Demo Code

Summary: Demo code for lift team is done.

It will need modifications to the timing values, but here is the finished demo code for the lift mechanism:

UPDATE: Changed the function set-up:

***********************************

#include <Wire.h>

#include <Adafruit_MotorShield.h>

#include "utility/Adafruit_PWMServoDriver.h"

Adafruit_MotorShield AFMS = Adafruit_MotorShield();

// Motor on M1 and M2

Adafruit_StepperMotor *BMotor = AFMS.getStepper(200, 1);

// Motor on M3 and M4

Adafruit_StepperMotor *FMotor = AFMS.getStepper(200, 2);

//Sets motor directions and speed

int up = FORWARD;

int down = BACKWARD;

int liftSpeed = 50;

int count = 0;

Update- Assembly and Parts Requested

Summary: Do not edit assemblies and the parts have been requested from the prototyping lab.

Jesse stayed up late last night fixing our broken assemblies and creating a change log to monitor the updates. In the interest of consistency and his sanity, when you model a new component upload it to the Google Drive with a separate assembly demonstrating how it fits together, and then Jesse will add it to the comprehensive file.

This morning I also requested parts from the rapid prototyping lab.

For 3D printing:
2 "shaft.SLDPRT"
2 "gearbox-axle.SLDPRT"
4 "Axle-bracket.SLDPRT"

For laser cutting:
8 "Actual Rack.SLDPRT"
4 "Actual Gear.SLDPRT"

If we need more parts, we need to submit them ASAP, especially if they are to be 3D printed.

One last note, remember we are not meeting tomorrow morning anymore, unless the parts are miraculously finished today. This does not mean we should not all upload some demo code to prove that we have not forgotten about the Arduino programing.

Full Group Meeting (11/19)- Little Bit of Everything

Summary: Assembling the body, finishing designs, and started coding.

We finished assembling our prototype body:

 Modeled more of the components:

We worked on finishing our slides for the presentation. See the Google Drive.

We began writing some demo code for the lifting mechanism, right now the motors do not turn in unison. I think it is because the first runs for 200 steps before the second one starts, but this is a start:

*************************************************

#include <Wire.h>

#include <Adafruit_MotorShield.h>

#include "utility/Adafruit_PWMServoDriver.h"

Adafruit_MotorShield AFMS = Adafruit_MotorShield();

// Motor on M1 and M2

Adafruit_StepperMotor *BMotor = AFMS.getStepper(200, 1);

// Motor on M3 and M4

Adafruit_StepperMotor *FMotor = AFMS.getStepper(200, 2);

int UP = FORWARD;

int DOWN = BACKWARD;

int SPEED = 50;

void setup() {

 

  AFMS.begin();

}

void loop() {

 

  //Lift Up 

  BMotor->setSpeed(SPEED);

  FMotor->setSpeed(SPEED);

 

  BMotor->step(200,UP,DOUBLE);

  FMotor->step(200,UP,DOUBLE);

 

  delay(2000);

 

  //Hold Position

  BMotor->setSpeed(0);

  FMotor->setSpeed(0);

 

  delay(2000);

 

  //Lower Down

  BMotor->setSpeed(SPEED);

  FMotor->setSpeed(SPEED);

 

  BMotor->step(200,DOWN,DOUBLE);

  FMotor->step(200,DOWN,DOUBLE);

 

  delay(2000);

 

  //Hold Position

  BMotor->setSpeed(0);

  FMotor->setSpeed(0);

 

  delay(2000);

}

*************************************************

(NOTE: You need the libraries I added to the Google Drive in order for this to work, unzip and place the whole folder inside C:\Users\Name\Documents\Arduino\libraries, this also contains a great example for using multiple motorshields together.)

Update: Supplies

Summary: Received motor shields and stepper motors, still waiting on the gearbox and battery holder.

We picked up the supplies they had received so far. The stepper motors we ended up with have slightly less holding torque, than we requested, but it should be fine.

 

The headers are all soldered on now, so we can do some coding tonight for the lift system (I put the libraries folder onto google drive).

Still waiting on everything from Pololu.

Update: Stairs Complete

Summary: Stairs are complete.

4 hours and a half sheet of plywood later, the stairs are complete! I will bring them to Lowell with me tomorrow. Here are some pictures:

The dimensions are: 8.25 inch risers with 9 inch treads. The two modifications I made were instead of being 3 feet wide, these are only 2, but that should be more than sufficient. I also incorporated a 1 inch nosing, because on steps that are less than 11 inches deep, a nosing is required.

They are nice and sturdy, so they should be able to hold whatever weight we need to put on them. Also, its good we'll have these because the presentation is in the Saab ETIC, not Cumnock.

Wheel Team - Gear Box

Summary: Today, we determined what kind of gearbox to use for the wheels. We settled on the Tamiya double gearbox from Pololu shown below. 

The two DC motors in this set are rated for 3-6V.The reason this gearbox was decided on was that is is light, it meets our requirement of being able to adjust the speed of each motor separately, and it can fit comfortably into our design for the base. One of the benefits of choosing this gear box is that it can be customized for several different gear ratios as shown in the picture below.





Something that will need to be addressed in the future is that the axles for this gearbox are likely to be too short, and will need to be extended. The two ways currently being considered to solve this are scavenging pieces from an erector set, or 3D printing extensions.

Another item that was discussed today is how we plan to power the arduino boards and the motors. It was decided that we will purchase two 4-AA battery holders from Pololu and wire them in series to power all of our boards.

Picture Links:
http://a.pololu-files.com/picture/0J258.1200.jpg?19fc391180b8b92adce3d97e9c62e8f8
http://a.pololu-files.com/picture/0J256.1200.jpg?32be6c1cf4f15c9806ac071db6e22f2a

Full Group Meeting (11/12)- Presentation and Scheduling

The presentation submission deadline is 11/21, which is next Friday (This might be an early submission deadline). The presentation should be 3-5 slides. We need a three minute presentation and a 10 minute presentation for the night of. The judging components are:

• Practicality (Michael)
• Creativity (Brendan)
• Marketability (Jesse and Shyam)
• Cost-effectiveness (Jesse and Shyam)
• Presentation (Everyone)

We are sliding back our design deadline, to account for the extra time we spent on building yesterday. We are also making the following additions to our calendar:

11/17 Monday- Individual SolidWorks Designs Due
11/19 Wednesday- Presentation Slides (Layout individual parts on the Google drive file)
11/21 Friday- Full Group Meeting (at 10 am) with Draft Arduino Codes and Individual Systems Fully Built

Our parts have been ordered, and should be arriving on 11/17. Side Note: In order to better facilitate the robot following a simple "Demo" path we are going to use a single Arduino as the control board.

The layout of the website was also updated from its minimalistic design.

Lift Team- Holding Mechanism

Summary: We prototyped/built the main body and discussed the lifting mechanism.

Based on our previous Solidworks models, we cut pieces of foam coreboard to form the body. Nothing was glued to allow for further cut outs to be made. Assuming the glued version is sturdy enough this can be our final body, otherwise we will laser cut identical parts out of acrylic.

Pictures:

We also discussed the lifting mechanism: DC motors would allow the body to move up, but would not hold it in place for loading or for climbing stairs. We could incorporate some sort of ratchet (see here) with a servo to release the hook, but this would further complicate the design. Additionally, this would allow for only an uncontrolled descent. A stepper motor will allow more advanced control and has a holding torque that is maintained as long as voltage is applied. We will use the Adafruit motor shields with the Sparkfun stepper motors.

These motors have a reported holding torque of 2.3kg*cm, which means that theoretically with two motors and a .5 inch diameter gear the robot can be supported as along as it is under 7 pounds.

Lift Team- Rack and Pinion Gear System Design

Summary: Gear design for Lift Team.

We developed solidworks models to provide a clearer demonstration of the initial sketches:

A crude initial served as the starting point:

We were then able to model out:

We simplified these sketches by using a cylinders instead of gears and not adding teeth to the rack yet, this can be updated later. We also still need to add a middle section with the motors and gears to turn the shafts. These files are on the Google Drive.

In order to hold the two layers together we had some ideas about a bracket that could have a bolt running through the entire body of the robot.

Wheel design - preliminary exploration

Progress on the wheel mechanism has gotten off to a great start. We have settled on a 4 wheel design with the two front wheels connected to two individual DC motors via a gear system. The back wheels will be connected to the base with swivel joints. The advantages of this design are many. First, it will be an easy system to program into the arduino. To turn our robot, we will only have to adjust the speed of one motor. For instance, to turn right, the right motor would be slowed. The back wheels will be attached by swivel joints so that when the front wheels are turning, the back wheels won't drag. The front wheels will be connected to the base via two separate axles, each connected to gear trains that connect to the motors. Another advantage is the sheer force provided by the integration of two DC motors, each providing a significant source of power. The third advantage to be found in such a design is the relative mechanical simplicity of the steering mechanism. Rather than building and programming a convoluted power steering system which requires the implementation of many separate moving parts, the drive is simply powered by two DC motors that speed up or slow down to provide a simple steering system.

Below is a visual representation of the DC motor/gear system used to drive the wheels.

The following picture is an idea for the type of wheels to be used. We are currently looking into LEGO pieces to provide the gears and axle for the front wheels.

-Shyam Sheth, Brendan Victor

Full Group Meeting (11/03)- Design Parameters and Division of Labor

Meeting Summary: Discussed design parameters in terms of the dimensions, set-up a project time table, and did some initial designing.

We will split the design and assembly into two main systems:

1. Lift Team- Michael and Jesse
2. Wheel Team- Shyam and Brendan

The individual pairings are responsible for designing their system and how it will mount onto these.

We are also splitting up the Executive Summary:

• Issue/Problem- Shyam
• Opportunity- Jesse
• Team's Solution-Michael/Brendan
• Feasibility- Michael/Brendan

Timetable:
We will have progress meetings every Wednesday from 6-8pm

11/05 Wednesday- Full Team Meeting
11/07 Friday- Finish Individual Parts of the Executive Summary
11/10 Monday- Executive Summary Due
11/12 Wednesday- Individual Systems Fully Designed
11/19 Wednesday- Individual Systems Completed
11/30 Sunday- Goal Completion Date
12/03 Wednesday- Last Day to Complete the Presentations (3 min and 10 min)
12/04 Thursday- Finish and Practice Presentations (3 min and 10 min)


Previously we had decided rectangular design instead of circular because it can be wider than it is long. It should have 4 wheels and 4 climbing pillars.

Front wheels need to be stationary and powered. We can power just two of the wheels and allow the others to rotate freely, unless that does not have enough power to move the vehicle, in which case we can power all of them.

Supplies:

• Power Supplies (#?)
• 2 Motor Shields (Ask Prof. Sullivan about borrowing these)
• Foam core board with cardboard tubes for the platform
• Cardboard for prototyping
• Plexiglass

We'll build a set of 2 steps with the dimensions: 31.5 inches Wide, 8.25 inches High, 9 inches Deep (Residential Building Code). Michael will hopefully build these this weekend. This will allow us to perfectly program the stair climbing, and will allow us to present in locations other than Cumnock.

In terms of lifting the legs, we can use lead screws but they will be expensive and cause a lot of friction. Actuators and air cylinders would also be too expensive. Pulleys might work: they would be unreliable when going down, but they would be quick and easy for going up. Rack and pinion would be a very realistic option.

In terms of materials for the base. Foam core is expensive for prototyping, and might break in use. Let's prototype in cardboard. The platforms could be made with foam core board supported with foil tubes or popsicle sticks, in the interest of weight.


The design will be layered with the motors and standing pillars in between two solid layers of foam core board that are attached together with card board tubes. We need to maximize the dimensions of the upper platform. The deciding factor for the size is the stair tread depth. The width is going to be less a factor of the tread width and more a factor of stability when it stands. We can determine the exact platform dimensions afterwards.

Make a slot for the plate with a cup holder in the middle of it. We can easily make this at the end and just install it on top.

The robot will move along a preset path with our custom made steps and maybe we will add an RC or automated feature afterwards.

Concept Model:

 Climbing Mechanism: