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 …