Q&A: Robotics Mentor and Champion

Peter Matteson, a Senior Project Engineer at Pratt & Whitney in East Hartford, CT, has a passion for robotics. We recently discussed how he became involved with mentoring a high school robotics team, the types of robots the team designs, and the team’s success.—Nan Price, Associate Editor

 

NAN: You mentor a FIRST (For Inspiration and Recognition of Science and Technology) robotics team for a local high school. How did you become involved?

Peter Matteson

Peter Matteson

PETER: I became involved in FIRST in late 2002 when one of my fraternity brothers who I worked with at the time mentioned that FIRST was looking for new mentors to help the team the company sponsored. I was working at what was then known as UTC Power (sold off to ClearEdge Power Systems last year) and the company had sponsored Team 177 Bobcat Robotics since 1995.

After my first year mentoring the kids and experiencing the competition, I got hooked. I loved the competition and strategy of solving a new game each year and designing and building a robot. I enjoyed working with the kids, teaching them how to design and build mechanisms and strategize the games.

The FIRST team’s 2010 robot is shown.

The FIRST team’s 2010 robot is shown.

A robot’s articulating drive train is tested  on an obstacle (bump) at the 2010 competition.

A robot’s articulating drive train is tested on an obstacle (bump) at the 2010 competition.

NAN: What types of robots has your team built?

A temporary control board was used to test the drive base at the 2010 competition.

A temporary control board was used to test the drive base at the 2010 competition.

PETER: Every robot we make is purposely built for a specific game the year we build it. The robots have varied from arm robots with a 15’ reach to catapults that launch a 40” diameter ball, to Frisbee throwers, to Nerf ball shooters.

They have varied in drive train from 4 × 4 to 6 × 6 to articulating 8 × 8. Their speeds have varied from 6 to 16 fps.

NAN: What types of products do you use to build the robots? Do you have any favorites?

PETER: We use a variant of the Texas Instruments (TI) cRIO electronics kit for the controller, as is required per the FIRST competition rules. The motors and motor controllers we use are also mandated to a few choices. We prefer VEX Robotics VEXPro Victors, but we also design with the TI Jaguar motor controllers. For the last few years, we used a SparkFun CMUcam webcam for the vision system. We build with Grayhill encoders, various inexpensive limit switches, and gyro chips.

The team designed a prototype minibot.

The team designed a prototype minibot.

For pneumatics we utilize compressors from Thomas and VIAIR. Our cylinders are primarily from Bimba, but we also use Parker and SMC. For valves we use SMC and Festo. We usually design with clipart plastic or stainless accumulator tanks. Our gears and transmissions come from AndyMark, VEX Robotics’s VEXPro, and BaneBots.

The AndyMark shifter transmissions were a mainstay of ours until last year when we tried the VEXPro transmissions for the first time. Over the years, we have utilized many of the planetary transmissions from AndyMark, VEX Robotics, and BaneBots. We have had good experience with all the manufacturers. BaneBots had a shaky start, but it has vastly improved its products.

We have many other odds and ends we’ve discovered over the years for specific needs of the games. Those are a little harder to describe because they tend to be very specific, but urethane belting is useful in many ways.

NAN: Has your team won any competitions?

Peter’s FIRST team is pictured at the 2009 championship at the Georgia Dome in Atlanta, GA. (Peter is standing fourth from the right.)

Peter’s FIRST team is pictured at the 2009 championship at the Georgia Dome in Atlanta, GA. (Peter is standing fourth from the right.)

PETER: My team is considered one of the most successful in FIRST. We have won four regional-level competitions. We have always shined at the competition’s championship level when the 400 teams from the nine-plus countries that qualify vie for the championship.

In my years on the team, we have won the championship twice (2007 and 2010), been the championship finalist once (2011), won our division, made the final four a total of six times (2006–2011), and were division finalists in 2004.

A FIRST team member works on a robot “in the pits” at the 2011 Hartford, CT, regional competition.

A FIRST team member works on a robot “in the pits” at the 2011 Hartford, CT, regional competition.

Team 177 was the only team to make the final four more than three years in a row, setting the bar at six consecutive trips. It was also the only team to make seven trips to the final four, including in 2001.

NAN: What is your current occupation?

PETER: I am a Senior Project Engineer at Pratt & Whitney. I oversee and direct a team of engineers designing components for commercial aircraft propulsion systems.

NAN: How and when did you become interested in robotics?

PETER: I have been interested in robotics for as long as I can remember. The tipping point was probably when I took an industrial robotics course in college. That was when I really developed a curiosity about what I could do with robots.

The industrial robots course started with basic programming robots for tasks. We had a welding robot we taught the weld path and it determined on its own how to get between points.

We also worked with programming a robot to install light bulbs and then determine if the bulbs were working properly.

In addition to practical labs such as those, we also had to design the optimal robot for painting a car and figure out how to program it. We basically had to come up with a proposal for how to design and build the robot from scratch.

This robot from the 2008 competition holds a 40” diameter ball for size reference.

This robot from the 2008 competition holds a 40” diameter ball for size reference.

NAN: What advice do you have for engineers or students who are designing robots or robotic systems?

PETER: My advice is to clearly set your requirements at the beginning of the project and then do some research into how other people have accomplished them. Use that inspiration as a stepping-off point. From there, you need to build a prototype. I like to use wood, cardboard, and other materials to build prototypes. After this you can iterate to improve your design until it performs exactly as expected.

Energy-Measurement AFEs

Microchip_MCP3913The MCP3913 and the MCP3914 are Microchip Technology’s next-generation family of energy-measurement analog front ends (AFEs). The AFEs integrate six and eight 24-bit, delta-sigma ADCs, respectively, with 94.5-dB SINAD, –106.5-dB THD, and 112-dB Spurious-Free Dynamic Range (SFDR) for high-accuracy signal acquisition and higher-performing end products.

The MCP3914’s two extra ADCs enable the monitoring of more sensors with one chip, reducing its cost and size. The programmable data rate of up to 125 ksps with low-power modes enables designers to scale down for better power consumption or to use higher data rates for advanced signal analysis (e.g., calculating harmonic content).

The MCP3913 and the MCP3914 improve application performance and provide flexibility to adjust the data rate to optimize each application’s rate of performance vs power consumption. The AFEs feature a CRC-16 checksum and register-map lock, for increased robustness. Both AFEs are offered in 40-pin uQFN packages. The MCP3913 adds a 28-pin SSOP package option.

The MCP3913 and the MCP3914 AFEs cost $3.04 each in 5,000-unit quantities. Microchip Technology also announced the MCP3913 Evaluation Board and the MCP3914 Evaluation Board, two new tools to aid in the development of energy systems using these AFEs. Both evaluation boards cost $99.99.

Microchip Technology, Inc.
www.microchip.com

Issue 284: EQ Answers

PROBLEM 1
Can you name all of the signals in the original 25-pin RS-232 connector?

ANSWER 1
Pins 9, 10, 11, 18, and 25 are unassigned/reserved. The rest are:

Pin Abbreviation Source Description
1 PG - Protective ground
2 TD DTE Transmitted data
3 RD DCE Received data
4 RTS DTE Request to send
5 CTS DCE Clear to send
6 DSR DCE Data Set Ready
7 SG - Signal ground
8 CD DCE Carrier detect
12 SCD DCE Secondary carrier detect
13 SCTS DCE Secondary clear to send
14 STD DTE Secondary transmitted data
15 TC DCE Transmitter clock
16 SRD DCE Secondary received data
17 RC DCE Receiver clock
19 SRTS DTE Secondary request to send
20 DTR DTE Data terminal ready
21 SQ DCE Signal quality
22 RI DCE Ring indicator
23 - DTE Data rate selector
24 ETC DTE External transmitter clock

 

PROBLEM 2
What is the key difference between a Moore state machine and a Mealy state machine?

ANSWER 2
The key difference between Moore and Mealy is that in a Moore state machine, the outputs depend only on the current state, while in a Mealy state machine, the outputs can also be affected directly by the inputs.

 

PROBLEM 3
What are some practical reasons you might choose one state machine over the other?

ANSWER 3
In practice, the difference between Moore and Mealy in most situations is not very important. However, when you’re trying to optimize the design in certain ways, it sometimes is.

Generally speaking, a Mealy machine can have fewer state variables than the corresponding Moore machine, which will save physical resources on a chip. This can be important in low-power designs.

On the other hand, a Moore machine will typically have shorter logic paths between flip-flops (total combinatorial gate delays), which will enable it to run at a higher clock speed than the corresponding Mealy machine.

 

PROBLEM 4
What is the key feature that distinguishes a DSP from any other general-purpose CPU?

ANSWER 4
Usually, the key distinguishing feature of a DSP when compared with a general-purpose CPU is that the DSP can execute certain signal-processing operations with few, if any, CPU cycles wasted on instructions that do not compute results.

One of the most basic operations in many key DSP algorithms is the MAC (multiply-accumulate) operation, which is the fundamental step used in matrix dot and cross products, FIR and IIR filters, and fast Fourier transforms (FFTs). A DSP will typically have a register and/or memory organization and a data path that enables it to do at least 64 MAC operations (and often many more) on unique data pairs in a row without any clocks wasted on loop overhead or data movement. General-purpose CPUs do not generally have enough registers to accomplish this without using additional instructions to move data between registers and memory.

HMI Development on Intelligent Displays

4dsystems_HRES4D Systems and Future Technology Devices International Limited (FTDI) (aka, FTDI Chip) recently introduced the 4DLCD-FT843. The intelligent display solution incorporates FTDI Chip’s FT800 Embedded Video Engine (EVE) with the subsequent introduction of two additional products. This combined product gives design engineers a foundation on which to quickly and easily construct human-machine interfaces (HMIs).

The first of these products is the ADAM (Arduino Display Adaptor Module). This 47.5-mm × 53.4-mm Arduino-compatible shield permits communication between the Arduino via the SPI. The shield is suitable for use with Arduino Uno, Due, Duemilanove, Leonardo, Mega 1280/2560, and Pro 5V. The shield’s micro-SD card provides the Arduino-based display system with ample data storage. The 4DLCD-FT843 can use the micro-SD card to retrieve objects (e.g., images, sounds, fonts, etc.). Drawing power from the Arduino’s 5-V bus, the ADAM regulates the 4DLCD-FT843’s supply to 3.3 V. The FT800 EVE controller can handle many of the graphics functions that would otherwise need to be managed by the Arduino.

The ADAM is complemented by the 4DLCD-FT843-Breakout. With a 26.5-mm × 12-mm footprint, this simple breakout module enables the 4DLCD-FT843 to be attached to a general host or breadboard for prototyping purposes. It features a 10-way FPC connection for attachment with the 4DLCD-FT843 along with a 10-way, 2.54-mm pitch male pin header that enables it to directly connect to the host board. Both products support a –10°C-to-70°C operational temperature range.

The EVE-driven 4DLCD-FT843 has a 4.3” TFT QWVGA display with a four-wire resistive touchscreen. It features a 64-voice polyphonic sound synthesizer, a mono PWM audio output, a programmable interrupt controller, a PWM dimming controller for the display’s backlight, and a flexible ribbon connector.

Contact 4D Systems or FTDI Chip for pricing.

4D Systems
www.4dsystems.com.au

Future Technology Devices International Limited (FTDI) (aka, FTDI Chip)
www.ftdichip.com

MCU-Based Experimental Glider with GPS Receiver

When Jens Altenburg found a design for a compass-controlled glider in a 1930s paperback, he was inspired to make his own self-controlled model aircraft (see Photo 1)

Photo 1: This is the cover of an old paperback with the description of the compass-controlled glider. The model aircraft had a so-called “canard” configuration―a very modern design concept. Some highly sophisticated fighter planes are based on the same principle. (Photo used with permission of Ravensburger.)

Photo 1: This is the cover of an old paperback with the description of the compass-controlled glider. The model aircraft had a so-called “canard” configuration―a very modern design concept. Some highly sophisticated fighter planes are based on the same principle. (Photo used with permission of Ravensburger.)

His excellent article about his high-altitude, low-cost (HALO) experimental glider appears in Circuit Cellar’s April issue. The MCU-based glider includes a micro-GPs receiver and sensors and can climb to a preprogrammed altitude and find its way back home to a given coordinate.

Altenburg, a professor at the University of Applied Sciences Bingen in Germany, added more than a few twists to the 80-year-old plan. An essential design tool was the Reflex-XTR flight simulation software he used to trim his 3-D glider plan and conduct simulated flights.

Jens also researched other early autopilots, including the one used by the Fiesler Fi 103R German V-1 flying bomb. Known as buzz bombs during World War II, these rough predecessors of the cruise missile were launched against London after D-Day. Fortunately, they were vulnerable to anti-aircraft fire, but their autopilots were nonetheless mechanical engineering masterpieces (see Figure 1)

“Equipped with a compass, a single-axis gyro, and a barometric pressure sensor, the Fiesler Fi 103R German V-1 flying bomb flew without additional control,” Altenburg says. “The compass monitored the flying direction in general, the barometer controlled the altitude, and the gyro responded to short-duration disturbances (e.g., wind gusts).”

Figure 1: These are the main components of the Fieseler Fi 103R German V-1 flying bomb. The flight controller was designed as a mechanical computer with a magnetic compass and barometric pressure sensor for input. Short-time disturbances were damped with the main gyro (gimbal mounted) and two auxiliary gyros (fixed in one axis). The “mechanical” computer was pneumatically powered. The propeller log on top of the bomb measured the distance to the target.

Figure 1: These are the main components of the Fieseler Fi 103R German V-1 flying bomb. The flight controller was designed as a mechanical computer with a magnetic compass and barometric pressure sensor for input. Short-time disturbances were damped with the main gyro (gimbal mounted) and two auxiliary gyros (fixed in one axis). The “mechanical” computer was pneumatically powered. The propeller log on top of the bomb measured the distance to the target.

Altenburg adapted some of the V-1’s ideas into the flight control system for his 21st century autopilot glider. “All the Fi 103R board system’s electromechanical components received an electronic counterpart,” he says. “I replaced the mechanical gyros, the barometer, and the magnetic compass with MEMS. But it’s 2014, so I extended the electronics with a telemetry system and a GPS sensor.” (See Figure 2)

Figure 2: This is the flight controller’s block structure. The main function blocks are GPS, CPU, and power. GPS data is processed as a control signal for the servomotor.

Figure 2: This is the flight controller’s block structure. The main function blocks are GPS, CPU, and power. GPS data is processed as a control signal for the servomotor.

His article includes a detailed description of his glider’s flight-controller hardware, including the following:

Highly sophisticated electronics are always more sensitive to noise, power loss, and so forth. As discussed in the first sections of this article, a glider can be controlled by only a magnetic compass, some coils, and a battery. What else had to be done?

I divided the electronic system into different boards. The main board contains only the CPU and the GPS sensor. I thought that would be sufficient for basic functions. The magnetic and pressure sensor can be connected in case of extra missions. The telemetry unit is also a separate PCB.

Figure 3 shows the main board. Power is provided by a CR2032 lithium coin-cell battery. Two low-dropout linear regulators support the hardware with 1.8 and 2.7 V. The 1.8-V line is only for the GPS sensor. The second power supply provides the CPU with a stable voltage. The 2.7 V is the lowest voltage for the CPU’s internal ADC.

It is extremely important for the entire system to save power. Consequently, the servomotor has a separate power switch (Q1). As long as rudder movement isn’t necessary, the servomotor is powered off. The servomotor’s gear has enough drag to hold the rudder position without electrical power. The servomotor’s control signal is exactly the same as usually needed. It has a 1.1-to-2.1-ms pulse time range with about a 20-ms period. Two connectors (JP9 and JP10) are available for the extension boards (compass and telemetry)..

I used an STMicroelectronics LSM303DLM, which is a sensor module with a three-axis magnetometer and three-axis accelerometer. The sensor is connected by an I2C bus. The Bosch Sensortec BMP085 pressure sensor uses the same bus.

For telemetry, I applied an AXSEM AX5043 IC, which is a complete, narrow-band transceiver for multiple standards. The IC has an excellent link budget, which is the difference between output power in Transmit mode and input sensitivity in Receive mode. The higher the budget, the longer the transmission distance.

The AX5043 is also optimized for battery-powered applications. For modest demands, a standard crystal (X1, 16-MHz) is used for clock generation. In case of higher requirements, a temperature-compensated crystal oscillator (TCXO) is recommended.

The main board’s hardware with a CPU and a GPS sensor is shown. A CR2032 lithium coin-cell battery supplies the power. Two regulators provide 1.8  and 2.7 V for the GPS and the CPU. The main outputs are the servomotor’s signal and power switch.

Figure 3: The main board’s hardware with a CPU and a GPS sensor is shown. A CR2032 lithium coin-cell battery supplies the power. Two regulators provide 1.8 and 2.7 V for the GPS and the CPU. The main outputs are the servomotor’s signal and power switch.

Altenburg’s article also walks readers through the mathematical calculations needed to provide longitude, latitude, and course data to support navigation and the CPU’s most important sensor— the u-blox Fastrax UC430 GPS. He also discusses his experience using the Renesas Electronics R5F100AA microcontroller to equip the prototype board. (Altenburg’s glider won honorable mention in the 2012 Renesas RL78 Green Energy Challenge, see Photos 2 and 3).

The full article is in the April issue, now available for download by members or single-issue purchase.

One of the final steps is mounting the servomotor for rudder control. Thin cords connect the servomotor horn and the rudder. Two metal springs balance mechanical tolerances.

Photo 2: One of the final steps is mounting the servomotor for rudder control. Thin cords connect the servomotor horn and the rudder. Two metal springs balance mechanical tolerances.

Photo 2: This is the well-equipped high-altitude low-cost (HALO) experimental glider.

Photo 3: This is the well-equipped high-altitude low-cost (HALO) experimental glider.