HotSpot: Thermal Seeking
Application
Real-World Design
In designing this project, we knew that it would ultimately be a proof-of-concept rather than finished product and so we took advantage of the prototyping materials and processes available to us. We implemented low-cost and immediately available solutions such as laser-cut plywood and household materials. For the electronics, we opted to employ an off-the-shelf microcontroller and breadboard rather than design our own PCB. While these choices did introduce a number of additional challenges, they also permitted us to rapidly explore new ideas.
Design Specification
System Constraints
Our most significant tradeoff in designing this robot was that of material cost with quality of motion. Although laser-cutting is significantly less expensive than other manufacturing methods, loose tolerances and inconsistent geometry can yield uneven motion. Because this application does not require impeccably smooth translation, we determined that the benefits of laser-cutting outweighed the costs.
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Another consideration which we faced in the robot design was the output of the actuators. In trying to maintain affordability, we selected a low speed, low torque stepper motor. Knowing that for this prototype high speed wouldn't be required, we determined that implementing motors with a minimal output would not be problematic.
Design Overview
Integrated Software
iPhone Application: As the main command center of the project, this application provides the following functionality: iPhone to RedBear bluetooth connectivity, iPhone to FLIROne camera communication, internal thermal image processing and a hotspot locating algorithm. Storing the majority of the data on a single platform allows for easy data manipulation while communicating with multiple devices. These factors allow for catalyzed development and smooth integration.
RedBear Micro Arduino: In order to move the stepper motors, the RedBear applies a sequence of pin output voltages. An Arduino sketch enables communication with the iPhone via bluetooth while simultaneously producing the voltage sequence to move the stepper motors; thus, the X- and Y-movement of the stage is controlled. An algorithm for defining the absolute location of the payload is integrated into Arduino, which is vital for determining path traversal to the next payload location.
Design Overview
Mechanical System
Stage: The stage is the framework that both provides support for the mechanical motion and defines the scan area. This assembly derives its stability from mortise and tenon joints as well as reinforcement brackets. An integrated gear rack on each of the longest sides provides the foundation for the X-directional motion while the legs define the scan height.
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Bridge: Housing the pinion gears which mesh with the rack, the bridge assembly traverses the X-direction. An axle spanning its length ensures that both drive pinions rotate at equivalent rates to prevent binding. Free-spinning wheels help distribute weight and reduce friction. Three stepper motors, mounted inside the bridge, deliver the necessary torque for powering the motion via indirect-drive. These motors receive commands from an arduino-based microcontroller which seamlessly orchestrates the two motions.
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Hat: The hat assembly is mounted to the top surface of the bridge, thus inheriting a high degree of structural integrity. This allows for construction from thinner material as well as the inclusion of lightening holes. A pair of stepper motors, one at each end of the hat, drive the Y-direction of motion via a belt and pulley mechanism. The same microcontroller that regulates the bridge motion controls the Y-translation.
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Payload: A traveller subassembly, iPhone, and FLIROne thermal camera comprise the payload. The traveller is coupled to the motion of the belt, and slides with low friction on plastic skis constrained to grooves cut into the base of the hat assembly. The traveller is outfitted with clamps to secure the iPhone while in motion. The FLIROne camera, plugged into the lightning port of the iPhone, faces downwards such that it can scan the region of interest.
Design Theory
Criteria
​Hardware
Modularity in mechanical design
Linear motion in X- and Y-directions
Scan area: 24" x 36"
Z-height of 13"
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Communication
Sensing, planning, & actuation
Integrated microcontroller
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Software:
Bluetooth enabled iPhone application
​Rendered and processed thermal images
Arduino as hardware command hub
​Locations mapping algorithm
