Teeny-Weeny Hardware Platforms That Get Up and Walk Around: Smart Dust, Microrobots, and Macrorobots Michael Scott, Brett Warneke, Brian Leibowitz, Seth Hollar, Anita Flynn, Sarah Bergbreiter, and Kris Pister UC Berkeley NEST Retreat, Spring 2002

Overview Smart Dust –Concept –Where we are now Microrobots –Concept –Where we are now Macrorobots –Concept –Where we are now Conclusions

NEST Retreat, Spring 2002 Overview Smart Dust –Concept –Where we are now Microrobots –Concept –Where we are now Macrorobots –Concept –Where we are now Conclusions

NEST Retreat, Spring mm Thick-Film Battery Solar Cell Power Capacitor Analog I/O, DSP, Control Sensors Passive Transmitter with Corner-Cube Retroreflector Interrogating Laser Beam Mirrors Active Transmitter with Beam Steering LaserLensMirror Photodetector and Receiver Incoming Laser Communication Smart Dust - Concept

NEST Retreat, Spring 2002 Smart Dust - Processes (CMOS) 13 state FSM controller ADC ambient light sensor Photodiode Sensor input Oscillator Power input Power TX Drivers 0-100kbps CCR or diode Optical Receiver 1mm 330µm What’s working – Oscillator, FSM, ADC, photosensor, TX drivers What’s kind of working – Optical receiver (stability problems lead to occasional false packets)

NEST Retreat, Spring 2002 Smart Dust - Processes (MEMS) 2.8mm 2.1mm CCR Accelerometer Solar Cells CMOS IC

NEST Retreat, Spring 2002 Smart Dust - Integration Solar Cell ArrayCCR XL CMOS IC 16 mm 3 total circumscribed volume ~4.8 mm 3 total displaced volume

NEST Retreat, Spring 2002 Smart Dust - Microcontroller 8-bit datapath, 12-bit addressing Dual program and data memories Load-store RISC-style 32 registers, but most are for special hardware interfacing –Five general purpose –Two autoincrementing –16-bit RTC –Five timers –Four config/status Laser reprogrammable System sleeps most of the time, but woken up by various timers Software support –Assembler –Cycle-accurate simulator w/power estimation –Compiler Common sensor node tasks are automated by the hardware –Receiver decodes packets Stores new code or data in memory Executes immediate instructions Allows message packets to be interpreted by the datapath –Transmitter Synchronous or asynchronous Can stream a block of memory –ADC interface has several modes ranging from automatically taking a sample, thresholding it, and storing it to memory to allowing full program control

NEST Retreat, Spring 2002 Smart Dust - Instruction Set Move, Move Immediate Load Store Add, add w/carry Sub, sub w/carry AND, OR, XOR, complement Compare, signed and unsigned Shift – one bit Bit set/clear/xor/test Branch, Always, zero, carry, no carry Call – direct and function pointers Software Interrupt Halt 1 cpi for all, but no pipelining Addressing modes –Direct –Register indexed Timers –Transmit –Receive – power up, check for signal –Sample sensor 1, 2 –Software wake-up

NEST Retreat, Spring 2002 Smart Dust - Peripheral Specs ADC –Consumes 1.8 uW at 10 kS/s (180 pJ/sample 23 pJ/bit) –8-bits, “information-on-demand” Optical Receiver –Consumes 26 uW at 375 kbps (69 pJ/bit) –Receives 50 nW (-43 dBm) optical signals (visible through near IR) –1 mrad transmit 50m req. 10 mW optical transmit power CCR Passive Transmitter –Consumes 350 pW at 175 bps (2 pJ/bit) –Requires laser interrogation beam which acts as the downlink beam as well Photosensor and 1-axis accelerometer integrated

NEST Retreat, Spring 2002 Overview Smart Dust –Concept –Where we are now Microrobots –Concept –Where we are now Macrorobots –Concept –Where we are now Conclusions

NEST Retreat, Spring 2002 Microrobots - Concept CMOS Chip Solar Cells, High Voltage Chip Motor and Linkages Chip Goal: Make silicon walk. Autonomous Articulated Size ~ 1-10 mm Speed ~ 1mm/s

NEST Retreat, Spring 2002 Microrobots - Processes CMOS Process National’s 0.25 micron 5 metal layer process High Voltage Electronics and Solar Cell process Fabricated in-house Demonstrated Solar Cells ~ 30 Volts Mechanical Linkages and Actuators Process –Glass Reflow Process

NEST Retreat, Spring 2002 Microrobots - Integration Thinned Solar Cell/High Voltage Chip Solar Cells/ High Voltage Legs and Motors CMOS Substrate Thinned CMOS Chip Leg Inchworm Motors Assembly Wire Bonds

NEST Retreat, Spring 2002 Microrobots - Test Results

NEST Retreat, Spring 2002 Overview Smart Dust –Concept –Where we are now Microrobots –Concept –Where we are now Macrorobots –Concept –Where we are now Conclusions

NEST Retreat, Spring 2002 Macrorobots - Concept Objectives: Use off-the-shelf components to build inexpensive and modular autonomous robots Take advantage of Rene motes and TinyOS for wireless networking and modularity Goals: Build 50 robots to test various distributed algorithms

NEST Retreat, Spring 2002 Macrorobots - Hardware Motor-Servo board interfaces any combination of two motors, servos, and solenoids to a toy car platform Sensor boards are currently being prototyped, including a whisker board for obstacle detection and a digital accelerometer (ADXL202) board for crude odometry Low-level software components written to abstract hardware Motor-Servo Board Whisker-Accel Board (Bottom) (Top)

NEST Retreat, Spring 2002 Macrorobots - TOS Components Abstract the hardware from the application (Ping-Pong) Allows use of separate platforms or sensors without having to change code (whisker v. accel, tank v. car) Simple applications written without worrying about hardware

NEST Retreat, Spring 2002 Overview Smart Dust –Concept –Where we are now Microrobots –Concept –Where we are now Macrorobots –Concept –Where we are now Conclusions

NEST Retreat, Spring 2002 Conclusions Projected milestones: Smart Dust –Microcontroller (10-bit addressing) – late March 2002 –12-bit addressing version to follow Microrobots –Integrated with dust mote – December 2002 Macrorobots –Several mobile motes – March 2002 –50 “intelligent” mobile motes – May 2002

NEST Retreat, Spring 2002 Aside - Optical Communications Large antenna gain (~1e6) Small radiator (mm scale) Spatial division multiple access (SDMA) Received power ~1/d 2 (vs. ~1/d 2  7 for RF) No FCC regulations/right-of-way constraints Rx and Tx can be the same beam Output efficiency –Optical Laser slope efficiency P overhead = 1µW-100mW –RF GMSK slope efficiency ~50% P overhead = 1-100mW Slope Efficiency True Efficiency P in P out P overhead RF Laser CCR 2km 100nJ

NEST Retreat, Spring 2002 Aside - Energy Comparisons Bluetooth –Transmit 1mW for 1ms - 1nJ/bit fundamental Tx cost. –Actual Tx, Rx power drain ~100mW - 100nJ/bit, 10s of meters? GSM –Rx power drain= ~200mW  2uJ/bit –Tx power drain= ~4W  40 uJ/bit, <10km Optical (laser) –10nJ/bit 1-10km –20pJ/bit 0-50m