Multidisciplinary Senior Design Project 08027 Wireless Assistive Control System
Agenda Overview of Topic Customer Needs Front End Filter Digital Signal Processor Wireless Communication System Proof of Concept (RC Vehicle)
Why? Advertise the Electrical Engineering Promote focus within engineering disciplines Biomedical sciences program Signal Processing Control Systems Proof of concept for later projects Proof of concept for later projects
Basic Needs and Requirements Robust Reliable Safe No chance of shock Completely non-invasive Simple to use Well documented
Front End The front end consists of the electrodes that are held in place on the person by a “glove” collecting signals produced by muscle contractions. These electrodes are connected to an amplifier. The amplifier sends the data to the filter and eventually wirelessly to our RC vehicle.
Design Decisions “GLOVE” TO BE PUT ON THE PERSON ELECTRODE AND CABLE PURCHASE AMPLIFIER REAL TIME DATA TRANSFER
Design Decisions: “Glove” Design • Customer Needs • Needed a glove type piece of apparel that would securely hold EMG electrodes in place while the user moved their arm. • Glove had to be aesthetically appealing, to have a “coolness” factor since it would be used by a department to recruit prospective students. • Glove needed to be strong, durable, and be able to survive extended periods of storage. • Glove also needed to fit a variety of body types and sizes. Aimed to fit 95th percentile.
Design Decisions: Development of Concepts for “Glove” • Arm muscles overlap. • Difficult to accurately place electrodes • Generates “cross-talk” between electrodes • Moved to a dual arm design with thumb and forearm electrode locations. • Simpler, more accurate electrode placement • Eliminates “cross-talk” • More intuitive control logic for an operator
Design Decisions: “Glove” Concepts • Full Length glove – elastic material (concept A) • Require S, M, L sizes • Glue EMG wires into place inside glove • Full Length glove – denim material (concept B) • Adjustable, like a batting glove • Stitch wire into fabric • Arm Bands w/ thumb hoop (concept C) • Nylon webbing bands • Run wires underneath bands • Velcro, clips, or slides for adjustability • Wrap sleeve w/ thumb hoop (concept D) • Flap of fabric that is wrapped around the arm • Stitch wires into fabric • Velcro to keep sleeve in place
Design Decisions: “Glove” Selection • Used the Pugh concept selection process outlined in class. • First matrix narrows the field and can provide ideas for improvement of particular concepts.
Design Decisions: “Glove” Selection • Second matrix provides concept scoring for increased resolution is need to differentiate between competing concepts • Weights are applied to the selection criteria based on the customer needs and priorities.
Design Decisions: “Glove” Materials Material Research: • Decided early on to make the arm strap design out of Nylon Webbing for several reasons • Strong • Flexible • Durable • Easy to work with manufacturing wise • Feels relatively comfortable to human skin • Found several websites that sold the material in bulk and “cut to length” quantities. • Also discovered Nylon Web Tubing.
Design Decisions: Electrode and Cable Purchase • Customer Needs • Electrodes and cables • need to be safe and sanitary. • need to be comfortable • Electrodes • need to stay in place and be applied easily. • need to be conductive enough to acquire an accurate signal. • need to be affordable.
Design Decisions: Electrode Selection • Active or Passive • Active: more expensive and larger • Passive: less expensive and flatter • Disposable or Reusable • Disposable preferred because reusable may be unsanitary • Also reusable all require an additional adhesive and conducting gel • (Comparison Chart: on next slide)
Need: Affordable Need: Sanitary Need: Safety
Design Decisions: Electrodes DDN-20 and DDN-30 Requires additional purchase of wires +Easy because they are attached with snaps - But will cost more 1024 and 1025 + 1025 comes with wires - $55 for 40 - 1024 requires alligator clips + $20 for 100 PT30 - Requires alligator clips + Most conductive: thick adhesive gel + Least expensive: $25 for 200
Design Decisions: Electrodes Samples requested Final Decision: Testing Hands on 1025 DDN-20 PT30 1024
Design Decisions: Real Time Data Acquisition Amplifiers Grass Technologies Model QP511 BIOPAC Systems Inc. Model MP30A BOTH tested safe via Fluke Biomedical 180 Connected to data acquisition device then to computer via USB NI-DAQmx will work with DAQ from National Instruments with MATLAB Free download adds library of commands for data acquisition Can be used to configure hardware. Includes example data acquisition programs
The Filter The filter is used to clean up the EMG data so that it can be processed more easily. The data is obtained from the data acquisition device and then processed in matlab. After the data is processed, it will be fed into the control system.
Design Decisions FILTER TYPE WINDOW TYPE
Design Decisions: Filter Selection • Analog • - Implementing • + Price • + Efficiency • - Versatility • Digital • + Implementing • + Price • + Efficiency • + Versatility
Design Decisions: Window Type • Hamming • + Stopband attenuation • + Raised cosine • Bartlett • - Stopband attenuation • Uniform • - Stopband attenuation
DSP PROCESSOR CHOICE CONTROL SYSTEM MODEL Control System Design Choices
DSP Processor & Development Board • BF531 – Development kit • + User friendly IDE • - GPIOs • + Cost of purchase (~$250) • BF537 – Development kit • + Cost (~$250) • + User friendly IDE • + GPIOs • TMS320C6455 -Development kit • - Cost (~$600) • + User friendly IDE • + GPIOs
Control System Model • Physical Model of the situation
Model Attributes • The model logic itself is inspired from Fuzzy Logic, however due to the lack of overlapping membership function full implementation of Fuzzy Logic is unnecessary.
Proof of Concept:RC Vehicle The RC Vehicle is a system acting in response to the sampled EMG data. It will act as a proof of concept for the other subsystems of the project. The vehicle will be controlled through a wireless communications link interfaced with the controller.
Design Decisions Hardware Platform Microprocessor selection Wireless Communications
Design Decisions: RC Vehicle Selection • Options: • 4WD1 – Robotics kit from lynxmotion.com • + Immediately available • + Simple to develop • - Poor Extendibility • - High cost of purchase (~$400) • Home-made RC vehicle • + Cost (~$120) • + Highly extensible • - Increased development time
Design Decisions: Microprocessor Selection • Options: • EZ 430 • + Low cost • + Faculty Familiarity • - Only 1 PWM • ATtiny2313 • + Low cost • + 4 PWMs • PIC 16F888 • + Low cost • + 2 PWMs
Design Decisions: Wireless Comm. Link • Zigbee (2006) • + Low cost • - 30 meter range • Sparkfun RF Link • + Low cost ~$17/pair • + Simple interface • + 150 meter range • - Low speed 4800 bps • Options: • Wifi 802.11x • - High cost ($200 each) • - ~30 meter range • - Complicated to interface with • Bluetooth Class 1 • + 100 meter range • - Cost ~$60 each
Specifications: Wireless Comm. Protocol Needs Provide direction and magnitude for Forward/Reverse Left/Right Discretely updated at defined interval
Specifications: Wireless Comm. Protocol • Restrictions • ATtiny2313 • 8bit registers • RF Link • Maximum ideal transmission speed: 4800bps
Specifications: Wireless Comm. Protocol • Right/Left Direction Control • 16 Positions • Forward/Reverse Direction Control • 16 Positions
In Summary • Overview of Topic • Customer Needs • Front End • Filter • Digital Signal Processor • Wireless Communication System • Proof of Concept (RC Vehicle)