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Grand Challenges for Autonomous Mobile Microrobots. Sarah Bergbreiter Dr. Kris Pister Berkeley Sensor and Actuator Center, UC Berkeley. What is an Autonomous Mobile Microrobot?. Size Total size on order of millimeters Mobility Should be able to move around a given environment
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Grand Challenges for Autonomous Mobile Microrobots Sarah Bergbreiter Dr. Kris Pister Berkeley Sensor and Actuator Center, UC Berkeley
What is an Autonomous Mobile Microrobot? • Size • Total size on order of millimeters • Mobility • Should be able to move around a given environment • Speeds of mm/sec • Autonomous • Power and control on-board • Communication between robots (?)
Applications for Autonomous Mobile Microrobots • Mobile Sensor Networks • Monitoring/surveillance • Search and rescue • Cooperative Construction • Assisted assembly • Sacrificial assembly
Ebefors, et al, 1999 Seiko, 1992 Hollar, et al, 2002 Yeh, 1995-2001 Sandia, 2001 Donald, et al, 2006 Previous Microrobots
1mm CCRs 1mm Solar Cell Array XL CMOS IC Smart Dust (Warneke, et al. Sensors 2002) Microrobots (Hollar, Flynn, Pister. MEMS 2002) COTS Dust (Hill, et al. ACM OS Review 2000) CotsBots (Bergbreiter, Pister. IROS 2003) Making Silicon Move Remove Legs Add Robot Body
1mm Why Is This So Hard? Power Mechanisms Integration Locomotion Actuators
1mm Challenge 1: Locomotion Locomotion
Challenge 1: Locomotion • Interaction with Environment • Obstacles are large • Reduce Complexity • Difficult to actuate out of plane • Difficult to fabricate bearings • Efficiency • Internal v. external work
Hopping Trajectory, Mass = 15mg, Angle = 60deg height (cm) distance (cm) Locomotion: Jumping
Locomotion: Comparison • What time and energy is required to move a microrobot 1 m and what size obstacles can these robots overcome? S. Hollar, "A Solar-Powered, Milligram Prototype Robot from a Three-Chip Process," in Mechanical Engineering: University of California, Berkeley, 2003. T. Ebefors, J. U. Mattsson, E. Kalvesten, and G. Stemme, "A walking silicon microrobot," presented at International Conference on Sensors and Actuators (Transducers '99), Sendai, Japan, 1999. http://asl.epfl.ch/index.html?content=research/systems/Alice/alice.php
Locomotion: Comparison • What time and energy is required to move a microrobot 1 m and what size obstacles can these robots overcome? A. Lipp, H. Wolf, and F.O. Lehmann., “Walking on inclines: energetics of locomotion in the ant Camponotus," Journal of Experimental Biology 208(4) Feb 2005, 707-19. S. Hollar, "A Solar-Powered, Milligram Prototype Robot from a Three-Chip Process," in Mechanical Engineering: University of California, Berkeley, 2003. T. Ebefors, J. U. Mattsson, E. Kalvesten, and G. Stemme, "A walking silicon microrobot," presented at International Conference on Sensors and Actuators (Transducers '99), Sendai, Japan, 1999. http://asl.epfl.ch/index.html?content=research/systems/Alice/alice.php
1mm Challenge 2: Actuators Actuators
Low Power Small Size Force/Displacement Efficient Simple Fabrication and Integration Power Supply Compatibility Robust Challenge 2: Actuators Yeh, 2001 Lindsay, 2001 Kladitis, 2000 Pelrine, 2002 Wood, 2005 Lu, 2003
k + - d V F t l Actuators: Electrostatic Inchworm Motors • High force at low power and moderate voltage • Accumulate short displacements for long throw • Fabricated in single mask process • Hollar inchworm designed for 500 mN of force and 256 mm of travel in ~ 2.8 mm2
1mm Challenge 3: Mechanisms Mechanisms
Challenge 3: Mechanisms • Simple Fabrication • Process Complexity • Batch v. Serial • Efficient • Friction • Robust • Matching to Actuators Hollar, et al, 2002 Wood, et al, 2003
2 months in the microlab, but very pretty! Mechanisms: Silicon
Orthogrippers fabricated in same process Parts rotated 90o and assembled out of plane Thermal actuators and rotation stages have been assembled Clamp w/o Assembled Part Clamp w/ Assembled Part Mechanisms: Assembly
1mm Challenge 4: Power Power
Small Mass and Volume Compatible with Actuators Any converter circuitry should be included Simple Integration Challenge 4: Power Cymbet Bellew, 2003 Roundy, 2003 Nielsen, 2003
Use isolation trenches to stack solar cells for higher voltages 0.5 – 100V demonstrated 10-14% efficiency Small Size Chip area: 3.6 x 1.8 mm2 Chip mass: 2.3 mg Complex Process Power: Solar Cells
1mm Challenge 5: Integration Integration
Need to connect all of the pieces Actuators, control, power supply, sensors, radio… Robust Compatibility Serial v. Batch Challenge 5: Integration Srinivasan, 2001 Last, 2006