Senior Design Project 12029 – RoboAnt

User’s Guide

Table of Contents

System Design 4

CAD Assembly 4

CAD Drawings 4

Manufacturing Information 9

Bill of Materials 10

Explanation of Components 10

Mechanical Assembly 12

Air Muscle Assembly 12

Leg Assembly 12

Cabling 12

Controls Assembly Information 13

Wiring Information 13

Solenoids 13

Circuit Board Assembly 13

Arduino Microcontroller 13

24 Volt Solenoid Battery 14

Operation 14

Ant Operation 14

Repair 14

Air Tank 14

Cables 15

System Design

CAD Assembly

Cad Drawings

Manufacturing Information

Should any of the machined parts be reproduced, these are some tips for remaking them.

a.  The aluminum plates were cut to size on the band saw and finished on the belt sander, holes were located with precision on the mill and slots were milled with an end mill (~700rpm and ~.02” per pass)

b.  The lexan pieces were cut on the band saw and drilled on the mill for more precise holes. The slots were milled with an end mill, larger passes can be made but care should be taken to avoid “gumming up” the tool.

c.  The lower legs were made by John Bonzo on the water jet to achieve the geometry needed.

d.  The upper legs’ radii were created by John Bonzo in the Brinkman lab. The holes that hold the lower legs were precision located and drilled on the mill, as were the holes that hold the vertical motion stop bolt. The slot was made by using a carbide end mill. A relief hole was made at end of the slot and ~.05” passes were made all the way through the part. The tab that connects to the cables was cut by the band saw and the holes were put in on the drill press. Finally, the hole that accepts the shaft that connects the top and bottom plate was drilled and reamed to get a precise .5” hole. The bushings were then inserted on the arbor press and reamed after insertion to achieve a precise .375” hole to accept the shaft.

Bill of Materials

Explanation of Components

1.  Air Tank- Used to provide air flow to the muscles.

  1. Purchased from Performance Paintball. Performance has Kurt Stratton’s name on file for tax exemption. Performance should be used to refill the air tank when it’s empty.
  2. This air tank was chosen because of its high capacity and well regulated flow rate. The tank is fairly cheap and accessible if it needs to be replaced or filled.

2.  Regulator- Used to control the amount of air that reaches the muscles

  1. Also purchased from Performance Paintball in a package deal.
  2. Chosen because of high flow rate and wide pressure range to reach the 60psi needed for the McKibben air muscles.

3.  Touch Sensors- Used in the controls to navigate the ant around obstructions

4.  Battery- Used to power the solenoids and relays

  1. Purchased at All-Battery
  2. Chosen because of NiMH’s ability to provide a large amount of milliamp hours at 24V with relatively low weight. The battery also comes with a charger for reuse.

5.  Arduino Board- Logic is flashed onto board to control the ant’s movement

  1. Purchased from Mouser
  2. Chosen because of ease of programming as well as the ability to re-program the chip easily and efficiently. This chip can be used many times for many different projects and the versatility of the Arduino board as well as the vast online resources allows conversion or retrofitting for future projects.

6.  Relays- Used to transfer commands from Arduino board to solenoids

  1. Purchased at Digikey
  2. Chosen because they perform their required task for relatively cheap cost

7.  Bushings- Minimize friction between shaft and shoulder as well as help transmit torques evenly over longer lengths of the shafts

  1. Purchased from McMaster
  2. Chosen because they’re impregnated with lubricant to reduce friction for a fairly low price. The bronze is also easily machinable and can hold tight tolerances.

8.  Shafts- Used to hold plates together and allow legs to rotate

  1. Purchased from Misumi
  2. Chosen for tight tolerances and the ability to order them pre-tapped to a specified length

9.  Air Hose and Fittings- Used for displacement through compression

  1. Attained through Dr. Lamkin-Kennard
  2. Chosen because of previous research from senior design groups

10.  Springs- Used to provide upward moment to support the ant’s weight

  1. Purchased through McMaster
  2. Chosen because of high spring constant to support weight.

Mechanical Assembly

Air Muscle Assembly

The air tubing is slid over two hard plastic ends, one that connects to the air source and the other that contains a metal eye hook for tying the cable. After the plastic pieces are slid into the tubing a plastic braided sheath is slid over the length to prevent over inflation. Finally hose clamps are placed over the plastic parts to keep the muscle tight and prevent any leaks. After the muscle is slid into the lexan base, the small, black, threaded to quick release connector is screwed into the air side of the muscle. It is very important to not over-tighten the black connector because it is very easy to sheer the threads off which renders the black connector and white plastic part useless.

Leg Assembly

There are a few different ways to assemble the legs but this is the easiest we’ve found. First, screw the shaft into the bottom plate with a small spacer that causes some separation between the shoulder and the top and bottom plates (this reduces binding of the shoulder). The larger tabs should be directly under the bottom plate and extend perpendicular to the length of the bottom plate. The center tabs should be slid further into the ant body to create more extension on the center springs, while the front and back springs should have much less extension (somewhere between the least amount of extension and the middle amount of extension). The tabs need to be very tight to ensure they don’t rotate or slide out. Then slide the shoulder over the shaft and screw the top plate onto the six shafts. Bend the hooks of the spring out to help slide them into their holes, attach the spring to the tab and then the lower leg. After the spring hooks are in their holes, re-clamp the spring hooks to ensure they don’t slip out of their holes. Then place the lower leg in the shoulder slot and use the shoulder bolt to lock it in. Then bolt in the stopper bolt to keep the leg from extending below the floor level. The smaller tabs should then be bolted to the top of the legs to extend the arm the cabling attaches to.

Cabling

The steel leaders that connect the muscles to their mechanical counterparts are held together with metal clamps. Feed the cable through the muscle’s eye hook and place the clamp over both ends of the clamp. It’s essential that the clamp is as tight as it can be to maintain taught cables. Then feed the cable through the routing eye hooks on the plate (if applicable) and place the metal clamp over the end of the cable. Then feed the cable through the part of the leg it is going to and feed the end of the cable back through the metal clamp. For the top 6 muscles that lift the legs, we found that slightly lifting the leg while clamping the cable can add some extra tightness when the leg is put back to its rest position. The lines should be tight enough to easily transfer the muscle motion to the leg, but not so tight that they add unnecessary stress to the muscle. There exists a cabling jig for wiring the rotational joints for the shoulders. This is located in the large cabinet in cubical 7 in the MSD Design Center. This jig allows all the shoulders to be wired in the same manner. Each muscle also features a tensioning nut. This allows the tension to be adjusted for each muscle for maximum performance.

Controls Information

Wiring Information

Solenoids

There are ten bundles of wires protruding from the bottom layer of the ant. Eight of these bundles are wrapped in orange wire sheathing while the other two are wrapped in blue wire sheathing. These bundles get connected to the wiring terminal strips on the top of the ant. These can be attaches after the top layer is connected to the bottom layer. It can be observed that four of the orange wire bundles have wires with labels while the other four have wires with no labels. The wires in each unlabeled bundle can be twisted together. These are the ground wires for the solenoids. These wires should be connected to the terminals labeled SG (See Figure 1). The rest of the solenoid wires should be reconnected in the manner displayed below in figure 1. If the ribbon cable has been disconnected from the terminal strips it should be reconnected using the diagram below.

Circuit Board Assembly

There are two Velcro strips on the front of the where the controls circuit board sits. Place the circuit board box so that the red alligator clip head is facing towards the rear of the ant. Also attach the male end of the ribbon cable coming from the center of the ant to the female end of the ribbon cable coming from end of the circuit board box.

Arduino Microcontroller

The Arduino sits on top of the circuit board box. Place it so the USB receptacle is facing towards the rear of the ant.

1.  First connect the white, black and green wires from the antennae to the Arduino. Connect the black wires to the pair of ground holes located next to pins 53 and 54. Connect the white wires to the pair of 5V holes next to pins 22 and 23. Connect the green wires to pins 8 and 9.

2.  Second connect the ribbon cable coming from the front of the circuit box to the bank of holes numbered 22 through 54. Support the Arduino board from the bottom and gently plug the ribbon cable plug into the bank of holes labeled 22 though 54. NOTE: This plug does NOT need to be plugged in all the way. It will be much more difficult to unplug if inserted all the way.

3.  Connect the red power wire and the black ground wire from the power switch and 9V battery plug. Plug the red wire into the Vin hole on the Arduino. Plug the black wire into the ground hole next to the Vin hole.

4.  Connect the black and white wires from the relay circuit board. These wires come from the top of the relay circuit board. Connect the white wire to the 5V hole in the same bank as the Vin hole. Connect the black wire to the ground hole near the 5V hole you just plugged the white wire into.

5.  If not already completed, connect the 9V battery to the 9V battery plug.

24 Volt Solenoid Battery

Remove any safety cover from the wires on the battery. Connect the red wire from the battery to the red alligator clip coming from the circuit board box. Connect the black wire to the terminal strip where the 24 volt ground wire is attached (See Figure 1).

Programming Information

Arduino Software

The Arduino software is available as a free download from arduino.cc. The programming language is similar to C++. There is a large library of code available from this website as well.

Arduino Code

The Code used to program the ant uses nested functions and a simple loop. The main run loop includes three functions. Walk A, Walk B and check sensors. Each of these as well as other sections of the code will be explained below.

Walk A and Walk B

Each of these pieces of code is a subfunction which lifts one set of legs, moves it forward and pulls the othe set of legs backward to propel the ant forward.

Check Sensors

This subfunction contains a section which checks the status of the bump sensors on the front of the ant. If either one of these sensors are compressed the code will revert to a reverse and turn sequence depending the sensor.

Reverse Code

This subsection of the code employs the same sub-blocks as the Walk forward code except the lifted leg set moves backward instead of moving forward. The Legs set which moves forward is not lifted in this instance as well.

Coding Sub-Blocks

There are multiple sections of code in the program which simplify the overall organization. Below is a lift of these sub-blocks of code.

·  LiftSetA

·  DropSetA

·  LiftSetB

·  DropSetB

·  SetAForward – All the legs in set A move into the forward position

·  SetAReverse – All the legs in set A move into the rear position

·  SetAClockwise – All the legs in set A move in a clockwise position

·  SetAAnticlockwise – All the legs in set A move in a counterclockwise position

·  SetAhorRelease – Releases all the horizontal muscles connected to set A

·  SetBForward – All the legs in set B move into the forward position

·  SetBReverse – All the legs in set B move into the rear position

·  SetBClockwise – All the legs in set B move in a clockwise position

·  SetBAnticlockwise – All the legs in set B move in a counterclockwise position

·  SetBhorRelease – Releases all the horizontal muscles connected to set B

Operation

Ant Operation

After the ant is assembled, the ant should be turned on by opening the air valve by turning the on/off control so that it is parallel to the regulator. The on/off switch for the electronics should then be flipped to the “on” position. It is very important to remember to turn both of those switches off when finished with operation because if left on, the battery or air will drain until empty. It is also important to check that the bump switches on the antennae aren’t engaged during operation.