This is an excellent video on this topic, kudos! You did a great job explaining the fundamental mechanics behind this style of mechanism. The link to the JPE Precision Point page is helpful as well. Thank you.
Dear content creator, Currently, as a master's student in mechanical engineering, I'm working on an assignment that involves designing a mechanism for linear movement with a stroke of 30 mm. My intention is to implement a parallel flexure guidance system and mitigate potential issues by incorporating an ancillary body. To ensure pure translation, it's crucial to actuate the mechanism at the force application point. My query is: What approach would you recommend for actuating such a system effectively? Best regards,
Hey Lesley, 30mm is fairly long, but still possible with flexures. To get good linear motion without rocking, I would recommend a double parallelogram structure here. The total system should be designed for +/-15mm of motion, and each stage can be designed for +/-7.5mm. My rule of thumb is that you want your beam to be 10-20X longer than the deflection at the tip, so think about 75-150mm long blades as a first pass. For the double parallelogram you want to actuate both stages in the middle of their flexures. There are a few options. One is to use reinforced blade flexures that have extra thickness in the middle (adds to stiffness faster than it subtracts from working range) and then drill a hole through that reinforced section to pass a screw/strut to push on the output stage. Another option is to make two sets of double parallelograms, space them apart out of plane, and then actuate between the two. The goal is to not apply forces out of plane to the flexure, as that will create parasitic torques and twists in your output. In terms of actual actuators, I would need to learn more. For static positioning, a leadscrew or even a long micrometer screw would be suitable. For more dynamic motions, a precision preloaded ballscrew can provide decent motion down to the single-digit micron level. For high velocity/high acceleration/high precision you will need a non-contact electromagnetic actuator like a voicecoil. The limits of positioning accuracy are often dictated by the position sensor used and the dynamics of the system. A double parallelogram would be very good for static positioning, but would suffer with high dynamic motion as the intermediate body is free to oscillate at a low frequency.
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This is an excellent video on this topic, kudos! You did a great job explaining the fundamental mechanics behind this style of mechanism. The link to the JPE Precision Point page is helpful as well. Thank you.
CRIMINALLY Underrated
beyond criminally
Great video!
Dear content creator,
Currently, as a master's student in mechanical engineering, I'm working on an assignment that involves designing a mechanism for linear movement with a stroke of 30 mm. My intention is to implement a parallel flexure guidance system and mitigate potential issues by incorporating an ancillary body. To ensure pure translation, it's crucial to actuate the mechanism at the force application point. My query is: What approach would you recommend for actuating such a system effectively?
Best regards,
Hey Lesley, 30mm is fairly long, but still possible with flexures. To get good linear motion without rocking, I would recommend a double parallelogram structure here. The total system should be designed for +/-15mm of motion, and each stage can be designed for +/-7.5mm. My rule of thumb is that you want your beam to be 10-20X longer than the deflection at the tip, so think about 75-150mm long blades as a first pass. For the double parallelogram you want to actuate both stages in the middle of their flexures. There are a few options. One is to use reinforced blade flexures that have extra thickness in the middle (adds to stiffness faster than it subtracts from working range) and then drill a hole through that reinforced section to pass a screw/strut to push on the output stage. Another option is to make two sets of double parallelograms, space them apart out of plane, and then actuate between the two. The goal is to not apply forces out of plane to the flexure, as that will create parasitic torques and twists in your output. In terms of actual actuators, I would need to learn more. For static positioning, a leadscrew or even a long micrometer screw would be suitable. For more dynamic motions, a precision preloaded ballscrew can provide decent motion down to the single-digit micron level. For high velocity/high acceleration/high precision you will need a non-contact electromagnetic actuator like a voicecoil. The limits of positioning accuracy are often dictated by the position sensor used and the dynamics of the system. A double parallelogram would be very good for static positioning, but would suffer with high dynamic motion as the intermediate body is free to oscillate at a low frequency.
It would take more than 5 degrees of constraint to prevent me from liking this video!
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