This robot has odd origins... I needed a test platform for the high power H-Bridge design I have come up with for the Neighborhood Roving Platform (NeRP) project. Given that the NeRP project has 10 of these integrated into a single design I thought it best to design and build a single functional module with which to test. Given that I have some motor / gearbox combinations here in the studio for use in a different project, a coworker of mine suggested that I produce a pair of the new amplifier boards, clamp the whole mess to a piece of plywood and test drive it around the studio floor.
Of course there are a number of other functions I need to integration test and if I am going to develop the PID functionality on this platform, then I'll need to integrate the IMU and several other functions. At this point the reader may be thinking feature creep, and that is exactly what this project is... It is a fun string of feature creep that turned a high powered motor driver board into a fully developed robot.
There is a lot more to share about tasks and foundations, and since this project shares a common lineage with the NeRP project (below) I encourage the reader to follow on on section 00 of that project.
The primary build of the ProtoBot project was started and completed in a single year, 2007. The electrical design of the five primary CCAs stated in December '06 over the Christmas Holiday. The mechanical fabrication started shortly there after in January and was continued on into late spring / early summer. Work was interupted for approx~2 months with my employer flying me around to the country to work with various customers and witness subcontractors product qualification testing. Yeah, sigh there is nothing worse being stuck in a hotel in the rainy months in Oregon when all of your hobbies are 1600 miles away, sigh... Upon returning, a few last small parts were finished-up and software integration and debugging began in Ernest. ProtoBot made its first public debut in Dallas, in Nov. of 2007. Subsequent software development and testing is an on-going task and will likely last a few additional years...
ProtoBot exists as a simple 4 wheeled robot with differential steering and no suspension components. Differential steering is implemented through the use of #35 stainless steel chain connecting the gearbox output to both wheels at the same time. As the structural plates are designed to be extremely simple to make they could just have easily have been cut from wood on a table saw. The only reason for the extensive lightening holes and extra material removal is to lighten the overall chassis.
The mast is a derivation of several previous designs and observations of armature roboticists who's work proceeded me. Their observations show magnetic effects of the fields of motors and other radiated EMI fields on stationary fields like the earth's magnetic field thus influencing the readings of magnetic compassrd and IMU's like the one by micro-strain that I will be using. Rather than spend a large amount of time shielding all of the various components it is much easier to merely separate the components with physical space. Additionally, the adjunct of the mast allows for the separation of the antenna of the two independent radio systems to keep their internal heterodynes from interfering with each other.
The primary objectives for ProtoBot as a stepping stone prototype in the design, build and test of NeRP are four fold:
- Characterize the motors and their expected performance as these same motors will be used in the propulstion systems for NeRP.
- Design, Fabricate and Test motor amplifier / drivers that can handle the high currents and required closed loop feedback.
- Develop a good protion of software base that can be refactored into the NeRP development.
- Integrate, test and characterize a number of sensors including:
- Sonar distance ranging
- Infra-Red distance ranging
- Global Positioning System
- Inertial Managment Unit
Even a simple test platform needs requirements. One of the biggest tricks to writing good requirements is to clearly state what we are going to build with-out stating how one is to go about building it. (what vs how) It is worth noting that in addtion, requirements specify the performance against which the verification, validation and testing (VV&T)can be measured. Finally, a good requirements capture allows one to define all the interfaces between the various subsystems and prior to detailed design work, asure compatability.
Max's Little Robot Shop is a one man operation with an end goal of having fun playing with robotics. As such the requirements captured here-in are necessarily 'light'. The goal here is to make sure the essence of the development task is captured and documented sufficnetly that the end project adequatly meets the need of the original request.
- All vehicle functions shall have full performance across specified environmental ranges.
- Vehicle shall operate in bright ambient conditions (up to 1,000F-l)
- Vehicle shall operate in dark ambient conditions (down to 0.01F-l)
- Vehicle shall operate in hot ambient conditions (up to 102deg-F)
- Vehicle shall operate in cold ambient conditions (down to 0deg-F)(including cold start)
- Vehicle shall be environmentally sealed to support operation in minimal inclimate weather conditions as defined below:
- Light sprinkling rain (<0.1-in/hr)
- Light snow (<0.5-in/hr)
- Mild blowing dust / dirt / detritus
- Typical machine shop ground based FOD
- Vehicle shall support fording of 3"(min) flowing water such as parking lot egress during rain.
- Vehicle shall support operation with slightly decreased performance requriements in grasses including woodland or field grasses to a height of 6~8-in.
- Vehicle shall support operation with decreased performance requirements in standing snow at depths up to 4-in.
- Mission ready vehicle shall weigh less than <100lbs(NTE).
- Mission ready vehicle shall fit with-in 3-ft x 3-ft x 3-ft bounding cube(NTE).
- Mission ready vehicle shall support onboard power system swap out in 3-min(NTE).
- Mission ready vehicle shall not contain any explosive, highly flammable or self igniting materials when exposed to strong electric fields or open spark.
- Mission ready vehicle shall not posses any materials preventing it from being shipped via freight carrier (ground or airborne).
- Mission ready vehicle shall not incorporate any controlled access technologies banned from export from the United States to either Canada or Mexico.
- Vehicle performance shall apply equally when traveling in a forward or reverse relative direction.
- Vehicle shall posses sufficent traction to engage 45-deg slopes (dry pavement) without slippage.
- Vehicle shall posses sufficent traction to engage 22.5-deg slopes (wet grass) without slippage.
- Vehicle shall posses sufficent power plant to accelerate its mission weight at 1/8G(min)
- Vehicle shall posses sufficent power plant to sustain controlled speeds of 4MPH for 1-hr continuous.
- Vehicle shall be capable of controlled operation at lower speeds down to 1-in/sec.
- Vehicle shall be capable of controlled turning on its center from a stop with-in a radius of 2-ft(NTE)
- Vehicle shall be capable of controlled turning at top missions sustained speed with an angular rate of 22.5-deg/sec(min)
- Vehicle shall be capable of controlled turns of 90-deg starting at top mission sustained speed in a radius not to exceed 16-ft.
- Vehicle shall maintain full speed and performance across the following terain.
- Flat level asphalt, concrete or other improved surface (wet or dry including inclines NTE 7.5%)
- Flat level grass, dirt, gravel or other unimproved surface (wet or dry including inclines NTE 7.5%)
- Vehicle may operate with reduced performance criteria across surfaces outside those listed above.
- Vehicle shall be capable of withstanding sustained random vibration to 1-G from 1Hz to 100Hz in all three primary axis.
- Vehicle shall be capable of withstanding sustained sinusoidal vibration to 5-G from 5Hz to 100Hz in all three primary axis.
- Vehicle shall withstand 18" of uncontrolled free fall. (vertical drop)
- Vehicle shall withstand repeated mission sustained high speed impacts with immovable objects. Rocks, Curbs, Houses, Fences, Trees, etc...
- Vehicle shall be capable of following a corrected straight line heading over a distance of 1000ft arriving at its destination with a angular deviation of (+/-)1-minute. (Improved surface)
- Vehicle shall be capable of traversing a corrected straight line heading over a distance of 1000ft arriving at its destination with a linear deviation of (+/-)3-feet. (Improved surface)
- Vehicle shall be capable of traveling to an arbitrary distant location. (with-in 1 mile)
- Vehicle shall be capable of navigating atonomously between pre-determined way points, NTE 1000ft in seperation.
- Vehicle shall be capable of autonomous identification of obstacles in navigation path.
- Vehicle shall be capable of autonomous circumnavigation of path blocking obstacles.
- Vehicle shall wait for path blockage to clear without circumnavigation if blockage is atonomously determined to be human.
- Vehicle shall support a primary navigation system update rate of 10Hz.
- Vehicle shall be capable of autonomous navigating to GPS cordinates in the real world.
- Vehicle shall be capable of autonomous identification of engineered external physical objects:
- Orange trafic cone, diet coke can, tennis ball, ping pong ball.
- Vehicle shall be capable of operating from standard gel cell batteries
- Vehicle power bus shall be 24V nominal.
- Vehicle shall operate with full performance as the power bus varies between 16V & 32V
- Vehicle shall posses onboard power system capacity to operate for 4-hrs of heavy usage between charging, primarily consisting of continuous navigation on unimproved terrain.
- Vehicle should posses onboard power system capacity to operate for 8-hrs of normal usage between charging, including loading, navigating, loitering and returning continuously.
- Vehicle shall provision for operation from bench power
- Vehicle shall provision for battery system recharge without battery removal
- Vehicle shall operate from bench supply during battery recharge
- Vehicle shall support hot swap between battery and bench power
- Vehicle shall facilitate software download / reprogram while on battery power or bench power.
- Vehicle shall protect on-board electronics packages from reverse installed batteries.
- Vehicle shall protect on-board power system from reverse connected power charging equipment.
- Vehicle shall protect on-board electronics packages from under-voltage operation. (both batery supplies and bench supplies.)
- Vehicle shall protect on-board electronics packages from over-voltage operation. (both batery supplies and bench supplies.)
- Vehicle shall protect onboard power supplies from over current events w/operational lockout.
- Vehicle shall posses backup fuse technology for power system bus protection in the event of catestrophic failure.
- Vehicle shall provide high speed transient suppression protection on main power busses.
- Vehicle shall operate with full performance in the presence of 1Vp-p ripple of any frequency 50Hz~10KHz on the power rails due to other as of yet unspecified power generation technologies.
- Vehicle shall provision extra carying capacity to double on-board power capacity / operational time.
- Vehicle shall provision for internal sensor interfaces.
- Vehicle internal sensors shall include 3-axis of temperature compensated gyros
- Vehicle internal sensors shall include 3-axis of temperature compensated accelerometers
- Vehicle internal sensors shall include 3-axis of temperature compensated magentometers
- Vehicle internal sensors shall include wheel encoders configured for 100-counts-linear in. (min)
- Vehicle internal sensors shall include motor driver current sense
- Vehicle internal sensors shall include internal power source level sensing.
- Vehicle internal sensors shall include power systems temperature sensing.
- Vehicle shall provision for external sensor interfaces.
- Vehicle external sensors shall include forward realtime color vision system
- Vehicle external sensors shall include realtime laser range finding system
- Vehicle shall demonstrate safe operation in the presence of spectators of any laser device Class IIB or higher
- Vehicle external sensors shall include [TBD] sonar sensors
- Vehicle sonar sensors shall posses a minimum sense distance of 9-ft.
- Vehicle sonar sensors shall posses [TBD]% coverage with [TBD]% granularity of the area in front of the robot.
- Vehicle external sensors shall include [TBD] infra-red sensing elements
- Vehicle external sensors shall include [TBD] thermal PIR sensors
- Vehicle external sensors shall include GPS radio and antenna
- Vehicle GPS system shall support standard NEMA messaging
- Vehicle external sensors shall include ground fall away sensing. (steep/deep ditches & trenches, stairs, etc...)
- Vehicle shall posses onboard data telemetry systems
- Vehicle data telemetry systems shall support 19.2K-baud(min)
- Vehicle data telemetry systems shall be bi-diretional
- Vehicle data shall be capable of reloading software across telemetry system
- Vehicle data telemetry application data shall be sensed from a distance of 2-miles
- Vehicle data telemetry systems shall incorporate forward error correction and data re-transmit upon unrecoverable error.
- Vehicle data telemetry system shall incorporate periodic "is-alive" or "heartbeat" function even while radio comms are in low power shutdown waking up for only minimal transmission, while maximizing power conservation.
- Vehicle shall posses local control telemetry system.
- Vehicle local control telemetry system shall provide e-stop functions
- Vehicle e-stop function shall inculude no-software between transmitter and motor disconnect.
- Vehicle local control telemetry system shall provide remote operator over-ride functions
- Vehicle local control telemetry system shall provide user light weigth hand held remote.
- Vehicle local control telemetry system shall incorporate in-advertent / malicious user lockout.
- Vehicle data and control telemetry systems shall be compliant with FCC rules Part 97 and all incorporated articles to the levels permitted for transmit by the primary operator.
- Vehicle shall support operation with telemetry systems disabled for operation by individuals not in possession of adequate licensing.
- Vehicle processing elements shall support field In System (re)Programablity.
- Vehicle embedded logic devices shall support field In System (re)Programability.
- Vehicle processing elements should support field remote In System (re)Programability.
- Vehicle processing elements should host memory storage to support terain mapping for areas of 1-mi x 1/2-mi.
- Vehicle processing elements should (where possible) incorporate standardized interfaces and comunications protocols.
- Vehicle processing elements shall provision for debug harness connections.
- Vehicle processing elements shall provision for 200% increase in processing capacity and memory storage.
- Vehicle processing elements shall collect and store vehicle internal and external operational state data for offline review.
- Vehicle processing elements shall make selected internal and external operational state data available for real-time analisys via telementry data link.
- Vehicle shall provision mass storage for data collection
- Vehicle mass storage shall be non-volatile
- Vehicle mass storage shall be 2Gb(min)
- Vehicle mass storage shall be expandable
- Vehicle mass storage shall be easily removable
- Vehicle mass storage, when removed, shall be PC file format compatible
- Vehicle mass storage shall have bandwidth to record continuous vehicle sensor data. (Approx 40Kbytes/sec)
- Vehicle shall posses user interface and debug display
- Vehicle debug display shall be capable of displaying 40(min) simultaneous data points (hex, ascii, int, float, etc)
- Vehicle debug display shall be capable of displaying 320x240(min) monochrome graphics.
- Vehicle shall posses rudimentary user input device to specify mission (at runtime) parameters.
- Vehicle shall provide warning indicators including but not limited to:
- Under / Over voltage lockout.
- Over Current Lockout.
- Over temperature drive system lockout.
- Human proximity stop
- BIT failure
- Fasteners used in vehicle construction shall be constrained to English thread call-outs
- Fasteners used in vehicle construction shall be the same fastening type (hex, slotted, phillips, torix, etc.)
- Diss-similar metal to metal contact of metals with highly different electron affinity shall be avoided. (Eg. aluminum & stainless steel)
- Wire connections used internal to the vehicle construction shall posess positive locking features.
- Wire connections used interfacing to off vehicle comunications channels shall implement low insertion force easy disconnect connectors to minimize accidental mission start without manual disengagement.
- Socketed components used in CCA level fabrication shall posses positive retention features.
- Power system and high current devices shall be subjected to 30%(min) component derating from worst case tolerance.
- Pressure vessels, if used in vehicle design, shall be capable of withstanding sustained loading of 4-times vehicle mission weight from any angle without breech or failure.
- Pressure vessels, if used in vehicle design, shall be capable of withstanding impact loading of 10-times vehicle mssion weight from any angle without breech or failure.
- Due to the high vibration environment all electromechanical interconnects shall use gold plated contacts with a minimum of 30micro-in of gold.
- To further extend high interconnect cycling and reduce the effects of vibration, anti-fretting compound shall be used on electro-mechanical interconnects.
- Vehicle shall incorporate bystander warning lights
- Vehicle shall incorporate bystander audible warning indicator
- Vehicle shall posses running lights for operation at low luminance
- Vehicle design shall minimize entanglement features. (Note, primary entanglement features for consideration are undergrowth, trees, shrubery and telephone pole guide wires.)
- Vehicle design should (where possible) provision for the software offload of data and processing intensive workload to specialized hardware constructs.
- Vehicle design data shall be maintained electronically.
- Vehicle design files shall document fully configuration of all electrical, mechanical, software and test to a level that reproduction of any deisgn portion (in part or in full) is easily acomplished.
- Vehicle design files shall be revision controlled and backed up no less than 1-time/wk.
- Vehicle design material choices and geometric relationships should, where possible, facilitate future modifications to add additional functionality / equipment. (Note: This requirement has far reaching impacts on the "functional" portion of the design, minimizing sculpted body panels, etc...)
- Vehicle design shall through the use of shielding, geometric constraints or seperation, prevent interferance between the multiple radio systems, sensors and propulsion elements known to cause destructive interference.
Nice to have:
- Vehicle should provision excess power to carry its own support equipment & tools given a substantial sacrafice in performance metrics.
- Vehicle should provision excess power to carry its operators support equipment & supplies given a substantial sacrafice in performance metrics.
- Vehicle should facilitate easy loading / unloading from transportation vehicle.
- Vehicle should operate quietly, not raising ambient SPL above 20dB(NTE) when measured at 36-in. (Note: This approximates rustling leaves in a breeze, or a calm room)
Future planned enhancments to the basic ProtoBot platform will included additional layered sensor suites, an arm for payload retrieval / delivery, a ping pong ball gun and a APU. Where possible provisions should be made to facilitate the staged design and integration of these applications. Consideration should be given to processing power and memory, power switching / interconnects and mechanical mounting points.
For those following the development of the robots on this site, the following outlines a short list of must visit related web sites.
- David Anderson's Robots (Robot: jBot)
- Jeff Sampson's Robots (Robot: Earth Explorer)
- Mark Curry's Robots (Robot: Intrepid)
- Dave Hylands' Robots (Robot: Orion)
- Ted Larson's Robots (Robot: Odessey)
- Scott Barlow & Tyson Messori' (CalPoly's Robots) (Robot: RoboMagellan)
- Nicholas Juliano (WSU Robotics) (Robot: Eddie)