Final Design
Final Design
Embedded Files
Performance
Performance
scan.movVideo of Device Performance
dropped.mp4Video of Scan from Camera
3D Topographical Results of Calibration Blocks
Chassis
Chassis
Final Design (Side)
Final Design
The final design selected is a large-footprint tripodal chassis frame that supports a motorized linear actuator that sweeps the laser triangulation assembly across the desired scanning area.
Tripodal design minimizes construction costs as well as instability due to any extra planar support points on uneven terrain.
The large footprint further improves stability.
Final Design (Side)
Final Design (Top)
The chassis is primarily constructed out of 45x45mm aluminum t-slot extrusions.
Two extrusion segments that connect to the central body using steel gussets
Lightweight extrusions
Total weight ~ 12 kilograms
A mixture of gussets, blind joints, and milling connectors are used to form the chassis frame.
Tensioning system connects each individual leg to increase structural stiffness and rigidity
Two eye bolts attached to the bottom of each leg, connecting ⅛ inch stainless steel cable
Turnbuckle for manually adjusting the cable tension
Turnbuckle an eye bolt for tensioning system. M8 eye bolts are slid into the leg extrusions and tightened into place
Actuator
Actuator
Actuation system (Side). Actuator attaches to the central 4590 chassis segment via a threaded mounting plate.
To ensure maximum stability, the linear actuator is mounted directly below the central chassis segment. The end of the actuator extends beyond the frontal edge of the main chassis segment so that there is room for the camera mount armature to fold towards the back leg of the chassis. Additionally, the selected line laser will never intersect or cross over the steel cable of the tensioning system at any point along the actuator stroke.
High load ratings as well as a high degree of repeatability
Allows for a scanning range of motion of 500 mm as per requirements
Ball screw provides smooth motion, and includes a dust cover to keep the shaft clean from debris
Motor: NEMA 23 2-phase, bipolar stepper with a torque curve matching the actuator's design input range.
Mounted to the actuator via an intermediate flange
Connects to the ball screw shaft using a flexible coupling
Leveling
Leveling
Left: Originally planned adjustable leg design. Right: Current workaround design consisting of a threaded rod and a threaded knob which serves as the foot.
Bubble Gauge
In order to maintain a level orientation for the actuator, adjustable height feet are attached to each of the legs, allowing for each foot to be adjusted by a minimum of 60 mm vertically. These feet consist of threaded rods with balls on the end which are inserted into each of the three legs, with a pair of nuts used for adjusting the rod length. A bubble gauge attached to the actuator mounting plate will allow the user to quantify whether or not the device is suitably level.
Electronics
Electronics
An onboard electronics housing sits on the central chassis segment
Contains microprocessor, PCB, stepper driver, and sensor package
Housing is also the location of the LCD screen that displays real-time parameters/manual rocker switch system
Easily detachable from the rest of the device due to the incorporation of a cable interface system
Power is provided by a portable power supply which uses a rechargeable lithium-ion battery
(Pictures of other electronic components can be seen in Multimedia Tab)
Sensor Integration PCB
Electronics Housing Interior
Triangulation/Calibration
Triangulation/Calibration
Staircase (left) and triangular (right) calibration blocks
Images used for obtaining calibration relation using staircase gauge. (Colors inverted for visibility)
Laser triangulation calculations are complicated and require knowledge of the camera’s and laser’s geometric information. With a modular design, it would be difficult to constantly have to change triangulation calculations based on different setups of the camera and laser as well as the specs of the mentioned parts. In addition, it would be tedious to have to measure the position of the parts with each small change. Because of that, calibration blocks were chosen to simplify the analysis portion of this process. These blocks allowed pixel data to be mapped to vertical height values relative to the referenced block With this streamlined process, the only dimensions/values that need to be known are the dimensions of the calibration block and the linear displacement between each camera frame.
Z: height of the laser point
u and v : the horizontal and vertical pixel distance between the laser beam centroid and the frame center
w and h : pixel width and height of the frame
FOV : field of view
d : horizontal distance between the camera and the laser
φ and θ: the camera and laser angle respectively
Laser Triangulation Principle and the Law of Sines
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