Wheelchair Mounted Dog Treat Dispenser Team Members : Zainab Abdullahi,Adam Dost, Gage Moore, Jachan Shrestha,Robby Wignall Faculty Supervisors: Dr.Nathalia Peixoto, and Dr.Kristine Neuber 1
Overview •About us Introduction •Purpose and Motivation •Design Architecture-Level 0 and Level 1 •Technology and System Wide Requirements •Detailed Design-Level 2 •System Models •Schematics and Part Selection •Prototyping and Progress •Potential Problems 2
About Us Name: Adam Dost Major: Computer Engineering Who I am: Studying Computer Engineering while actively studying the art of delegation. What I do: Senior Azure Cloud architect of the USAF Cloud1 initiative 3
About Us Name: Jachan Shrestha Major: Electrical Engineering Who I am: Electrical Engineering Senior at George Mason University. I was born and raised in Kathmandu, Nepal. What I do: Currently full time student 4
About Us Name: Zainab Abdullahi Major: Electrical Engineering Who I am: Senior Majoring in Electrical Engineering. I was born in Fairfax, Virginia and raised in Egypt What I do: Intern at Pepco Holdings Inc 5
About Us Name: Robby Wignall Major: Electrical Engineering Who I am: Pursuing second bachelor’s degree at GMU afuer receiving BS in Applied Mathematics from VCU. What I do: Intelligent Transportation Systems Project Manager for multi-million dollar projects. 6
About Us Name: Gage Moore Major: Electrical Engineering Who I am: Currently a senior studying Electrical Engineering with a minor in Computer Science, and a concentration in Computer Engineering. Employer: Patent Intern Pillsbury Winthrop Shaw Pittman LLP 7
Mission Statement The device shall assist people with disabilities to provide treats to their service dogs. 8
Situation Review People with disabilities who are wheelchair ● bound and accompanied by service dogs account for 0.9 percent of the U.S. population [1]. These dogs go through extensive training and ● annual tests. Rewarding the dog is essential for it to maintain ● maximum performance! 9
Past 492 Designs Not food safe ● Difficult to reproduce and rebuild ● Prone to break easily ● Jamming ● [2] 10
Past 492 Designs Size itself was too large ● Difficult in controlling dispenser output ● However this design’s procurement was fairly simple and done all in one store. [2] 11
Past 492 Designs Dispensed bowl size was fairly too ● small Coating the materials would incur a ● cost not available to the project team However the design was successful in its placement in the wheelchair. And had a safe location for the arduino to be stored. [2] 12
Previous Designs & Patents Problems with Previous Designs: 1. Not wheelchair adaptable [3-11]. 2. Not easily activated [4-10]. 3. Too large [3], [7]. [7] 4. Mechanical [3-10]. 5. Not food safe [11]. [3] 13 [11]
Patent Analysis/Need for Redesign Elements in Common with our Design: [10] 1. Button. [5] 2. Rotational Tray. [10], [11] [5] Using these common elements in combination [11] with our design should not yield infringement . 14
Requirements Review Functionality Must hold a cup of dog treats at a minimum ● Operational Shall operate while mounted on a wheelchair and safely dispense user requested ● amount of treats Input & Output Shall receive input from the operator and translate to actions. ● Materials Shall be food safe and eco-friendly. ● 15
Short Review (Continued) Previously, there were four possible designs. Design 1 A and 1B that utilize passive electrical components 16
Short Review (Continued) Design 2 A and 2B utilizing a microcontroller with more diversified functionalities. 17
Our Solution The key to an autonomous treat dispenser is the dispensing mechanism itself. All dispensing mechanisms are dependent on energy transfer, such as the kinetic energy from a spinning motor. We have decided to go with a rotary-based mechanism. 18
Our Solution 555 Timer Based Design Microcontroller Based Design 19
Design Architecture Level 0 20
Design Architecture Level 1 21
Background Knowledge/Phenomenology Servo Motor Analysis The following system model will be used to analyze the servo motor [12] Where the steady equations are: ei = iaRa + KeVm (Voltage equation) T = Torque = iaKT = J α (Torque equation) 22
Background Knowledge/Phenomenology Servo Motor Analysis The following system model will be used to analyze the servo motor [12] La = Motor winding inductance (Henries) eI = Applied voltage (Volts) Ra = Armature resistance (ohms) ia = Armature current (amps) TL = Load torque (lb-in) JT = Total inertia of motor armature plus load (lb-in-sec2 ) Vm = Motor velocity (rad/sec) Ke = Motor voltage constant (v/rad/sec) α = Acceleration (rad/sec2 ) KT = Motor torque constant (lb-in/A) 23
Background Knowledge/Phenomenology 555 Timer Analysis Astable: No “stable” state; the output is a square wave with period and duty cycle determined by the values of resistors and capacitors in the circuit. Monostable: When the 555 IC’s connection to the Trigger pin goes low, the output goes high for a certain amount of time as determined by the impedance of the circuit. Bistable (Schmitt Trigger): Similar to Monostable mode, but the output will remain high until the input to the Reset pin goes low. For the treat dispenser application, Astable or Monostable operation should be used. 24
Background Knowledge/Phenomenology Astable Operation As mentioned previously, this circuit’s output will generate a square wave with controllable frequency and duty cycle. This mode may be useful for activating a motor and dislodging treats. [14] Here, the period, T, is given by the sum of the time the output is high and the time the output is low (T = T_h + T_l), and T_high = 0.7 * (R1 + R2) * C1 T_low = 0.7 * R2 * C1 Duty Cycle = 100 * [T_h/(T_h + T_l)] 25
Background Knowledge/Phenomenology Monostable Operation This operating mode gives an output that stays high for a certain amount of time afuer being triggered. It can be cut short by reset or remain high with a “long push.” [14] Active output time T afuer a trigger can be found by: T = 1.1 x R1 x C1 An Resistor and Capacitor pair will then be used to achieve the required T for the treat dispenser to operate. 26
Background Knowledge/Phenomenology Power Analysis 555 Timer Microcontroller 555 Timer Chip - 50uA waveform The Raspberry Pi Zero W requires a ● ● 1.2A/5V Input which will draw 6W Motor ~4W per activation [17]. ● of power for the microcontroller Max. stall current - 650mA at 6V ● [18]. which will be at around 4W. The final estimate of each sensor ● The team will also leverage ● will add around 5W and the clicker additional LED’s and sensors each activation will also draw around 5W estimating to be around 5W per as well. addition. The final estimation of The final estimation of the total the total power consumption will ● range from 26-36W total. power consumption will range from 20-30W total. 27
Background Knowledge/Phenomenology Dispensing Analysis If we want the wheel to turn ⅓ of the way to dispense the treats, the distance needed to turn is given by: ⅓ * (2π r ) = ⅔ * π r Therefore, Circumference of Motor Gear = C_motor = ⅔ * π r Since gears are being used as shown in the Detailed Design portion, the outer diameter will be C_motor (to the gear tips) while the inner diameter should be large enough for the gear to turn the wheel. 28
Background Knowledge/Phenomenology Servo Motor Timing Analysis We can take the specified RPM for the Servo motor and figure out how long it will take to rotate around one time as: Rotation_time = RPM / 60 This Rotation_time will then be used to design the 555-timer circuit as well as the code for the microcontroller. The output from both of these designs should stay high for Rotation_time afuer an activation. 29
555 Timer Schematic 555-Timer Circuit in Astable Operation 30
555 Timer Operational (No Load) 555-Timer Circuit in Astable Operation - Total Current 31
Astable Output 555-Timer Circuit in Astable Operation - Output Pin 3 Waveform 32
Background Knowledge/Phenomenology Raspberry Pi Raspberry Pi’s are an inexpensive “off the shelf” solution that is readily available and easy to acquire. For the treat dispenser project we wanted to target all of our resources that could be acquired immediately and not need to be special ordered or made. With the small form factor (66.0mm x 30.5mm x 5.0mm) it will allow us to insert the part without causing intrusion. 33
Detailed Design (Level 2) 555 Timer Microcontroller 1. Use 555 timer to 1. Use recorded “click” generate “click” sound sound 2. Use small output 2. Output this signal to speaker speaker 34
Detailed Design (Level 2 continued) 35
Detailed Design (Level 2) 555 Timer Microcontroller 1. Use time delay via 1. Use a time delay loop to capacitor to spin motor generate the time delay for a time constant 2. Use Raspberry Pi 2. Use 555 timer to libraries to spin the generate the driver motor the correct signal for the motor distance 3. Reset motor control unit 3. Function will reset as it (555 timer) by sending acts on a generated setting reset to high interrupt from the user voltage pressing a switch 36
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