Stepper motor control limits

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One of the fundamental questions that arose during the control and testing of the SCARA arm was what is the maximum speed achievable and the torque available at that speed. Some digging around in the world-wide-web revealed the following: The speed is limited by the torque availability from the stepper to rotate. For steppers, as the torque drops exponentially with …

Achieving rotational accuracy with steppers

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For the SCARA (Selective Compliance Articulated Robot Arm) that I’m building for the course project, the rotation accuracy at the joints is critical to achieving overall accuracy. The stepper motors that I have are 200 steps per revolution which amounts to 1.8 deg per step. The accuracy is +/- 5% which means a rotational angle uncertainty of 0.18 deg (best possible). …

Harmonic Drives

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Harmonic drives (also called strain wave gear) was invented in 1957 by C.W. Musser. They offer several advantages over conventional gear systems, especially for high precision and high torque applications. Hence, they are commonly used in many industrial robots. High gear reduction ratios are possible in a small volume from 30:1 up to 100:1 in some cases! The patents regarding this …

How smoke detectors work

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Recently when I was cooking in my home, some of the food spilled over from the vessel and came in contact with the heating element giving rise to a dense smoke with the smell of burnt food like charcoal! Then the alarms inside our house went off! After a while,the smoke left the building through the windows and the alarms …

Precision couplings

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In one of my research meetings with my advisor, Prof. David Trumper, we were discussing about motors and motor couplings. He mentioned about how the metal bellows for precision couplings are manufactured using electroforming process. I did some more search on the topic, and found that they are very useful torque transmission elements which are very rigid torsionally and accommodate misalignments in …

How are ball bearings made?

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When I was making the Kinematic Coupling for Lab-4, I was wondering how I would manufacture the wooden balls. In the first day of class, Prof. Slocum had given us a wooden hemisphere which looked almost perfect. The most number of balls that are used anywhere in the world is in ball bearings. They are mostly made out of steel, but …

Seek and Geek – 2: Robots to manipulate work-volumes at a large distance from location of base actuators

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In my project, I’m trying to build a cell-sorter, primarily focussed on picking and sorting of islets. One of the major constraints in the design are that the work are is under the objective lens of the microscope. Thus all actuators should be outside this field area, yet resulting in motion accuracy of ~ 25 um. The are two major …

Seek and Geek – 2: Robots to manipulate work-volumes at a large distance from location of base actuators

admin 2.77, 2.77 Seek and Geek Leave a Comment

In my project, I’m trying to build a cell-sorter, primarily focussed on picking and sorting of islets. One of the major constraints in the design are that the work are is under the objective lens of the microscope. Thus all actuators should be outside this field area, yet resulting in motion accuracy of ~ 25 um. The are two major …