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Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

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Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#31

Post by nradov »

dsfyu404ed wrote: post #25
nradov wrote: post #12

Earlier quoted context omitted.

All else being equal, cars with CVTs are usually more fuel efficient than with other types of transmissions.

Because they're tuned to perform in a manner that delivers the maximum fuel economy in order to drag up the fleet average, driver experience be damned.

What's wrong with the driver experience? Mine seems fine. It's certainly better than the automatic transmission in my old car due to smooth and instantaneous power delivery with no "dead spots" for shifting between gears.

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#32

Post by mikepurvis »

I don't think the article mentions this, but being able to vary speed like this leads to some interesting possibilities around centralizing power plants— for example, being able to do a diff-drive or mecanum/omni platform with just a single large motor rather than multiple smaller ones.

The responsiveness probably wouldn't be there for this application, but I'm also curious about whether this could be made to work for a longer range gas/hybrid quadcopter.

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#33

Post by Animats »

This is cute, but the use case in robotics is questionable. A variable ratio transmission for a robot seems to solve a problem nobody has. Electric motor control today is able to do that job over a wide torque and speed range. From drones to electric cars to Diesel-electric locomotives, nobody uses variable-speed gearboxes much any more. There are many robot gearboxes, but I've never heard of one with a shifter. Machine Design has ads for robot gearboxes, including ads from Harmonic Drive, but they're all fixed ratio.

This thing would need a second motor to adjust the speed change, with an encoder, plus encoders on the input and output ends of the transmission. Something has to control all that.

If you need sudden bursts of high torque, overload the motor while monitoring temperature. You can run electric motors far above their continuous rating for brief periods, and if temperature is monitored, this is safe. That's how Tesla's "launch mode" works.

Not seeing the use case for this thing in robotics.

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#34

Post by fiter »

ggm wrote: post #19

Like a lot of mechanical contrivences, if you come from a world of digital 'machines' you're tempted to say but F R I C T I O N.. The thing is that clutches, gears, back-chatter, teeth wear, this is all bread-and-butter to mechanical engineers, this stuff has been well known for years. If these people have managed to package things into an assembly which is tractable, repairable, can be scaled, and suits their purpos…

If anyone is curious, the wheels that the parent poster is referring to are often called Mecanum wheels[0].

[0] https://en.m.wikipedia.org/wiki/Mecanum_wheel

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#35

Post by Mithaldu »

Animats wrote: post #33

This is cute, but the use case in robotics is questionable. A variable ratio transmission for a robot seems to solve a problem nobody has. Electric motor control today is able to do that job over a wide torque and speed range. From drones to electric cars to Diesel-electric locomotives, nobody uses variable-speed gearboxes much any more. There are many robot gearboxes, but I've never heard of one with a shifter. Mach…

How do you feel about his claim that this would be good for energy efficiency?

Or the claim that this would allow for easier human-safety by having the torque, if lowered, not be dependent on logic, but on the actual mechanics, making it possible to stop the entire system if a failure in the torque-change motor is detected?

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#36

Post by Animats »

Mithaldu wrote: post #35
Animats wrote: post #33

This is cute, but the use case in robotics is questionable. A variable ratio transmission for a robot seems to solve a problem nobody has. Electric motor control today is able to do that job over a wide torque and speed range. From drones to electric cars to Diesel-electric locomotives, nobody uses variable-speed gearboxes much any more. There are many robot gearboxes, but I've never heard of one with a shifter. Mach…

How do you feel about his claim that this would be good for energy efficiency? Or the claim that this would allow for easier human-safety by having the torque, if lowered, not be dependent on logic, but on the actual mechanics, making it possible to stop the entire system if a failure in the torque-change motor is detected?

How do you feel about his claim that this would be good for energy efficiency?

It's unproven. If you have to haul more mass around, that's worse for energy efficiency.

easier human-safety by having the torque (limited)

There are mechanical 'fuses' for torque limiting.[1] Having a transmission that can downshift into a very high torque mode is probably worse for safety. If torque is directly proportional to motor current, there are lots of standard safety devices for limiting motor current.

[1] https://www.mayr.com/en/products/torque-limiters

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#37

Post by Mithaldu »

Animats wrote: post #36
Mithaldu wrote: post #35

Earlier quoted context omitted.

How do you feel about his claim that this would be good for energy efficiency? Or the claim that this would allow for easier human-safety by having the torque, if lowered, not be dependent on logic, but on the actual mechanics, making it possible to stop the entire system if a failure in the torque-change motor is detected?

How do you feel about his claim that this would be good for energy efficiency? It's unproven. If you have to haul more mass around, that's worse for energy efficiency. easier human-safety by having the torque (limited) There are mechanical 'fuses' for torque limiting.[1] Having a transmission that can downshift into a very high torque mode is probably worse for safety. If torque is directly proportional to motor curr…

Interesting, thanks for expanding. If you don't mind another question:

> a transmission that can downshift into a very high torque mode

I'm missing something here i guess, how is this different from a motor that can deliver full torque just because the logic chip is driving it at full power? Is it because the motor wouldn't be able to reach such high torque in the first place? (Which might be a point in favor of the transmission.)

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#38

Post by kodfodrasz »

Mithaldu wrote: post #35
Animats wrote: post #33

This is cute, but the use case in robotics is questionable. A variable ratio transmission for a robot seems to solve a problem nobody has. Electric motor control today is able to do that job over a wide torque and speed range. From drones to electric cars to Diesel-electric locomotives, nobody uses variable-speed gearboxes much any more. There are many robot gearboxes, but I've never heard of one with a shifter. Mach…

How do you feel about his claim that this would be good for energy efficiency? Or the claim that this would allow for easier human-safety by having the torque, if lowered, not be dependent on logic, but on the actual mechanics, making it possible to stop the entire system if a failure in the torque-change motor is detected?

Actually the gear shifting would also be done by logic, so nothing gained by that.

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#39

Post by Mithaldu »

kodfodrasz wrote: post #38
Mithaldu wrote: post #35

Earlier quoted context omitted.

How do you feel about his claim that this would be good for energy efficiency? Or the claim that this would allow for easier human-safety by having the torque, if lowered, not be dependent on logic, but on the actual mechanics, making it possible to stop the entire system if a failure in the torque-change motor is detected?

Actually the gear shifting would also be done by logic, so nothing gained by that.

Not quite. In order to lower the torque on a stepper motor you need to have the logic controlling the motor control the torque for every single step the motor takes and that can switch from low to high between two steps. You can ward against this either with continuously checking logic or the torque limiters Animats mentioned: https://www.mayr.com/en/products/torque-limiters

If the inception drive is set to low torque a second motor needs to actively set it to a higher torque, which you can guard against by cutting power to the second one while in low torque mode, and having mechanical interlocks that cut power entirely if the shape of the drive changes to a high torque configuration while it's supposed to be low torque. Neither of these require continuous logic.

Re: Inception Drive: A Compact, Infinitely Variable Transmission for Robotics

#40

Post by kodfodrasz »

Mithaldu wrote: post #39
kodfodrasz wrote: post #38

Earlier quoted context omitted.

Actually the gear shifting would also be done by logic, so nothing gained by that.

Not quite. In order to lower the torque on a stepper motor you need to have the logic controlling the motor control the torque for every single step the motor takes and that can switch from low to high between two steps. You can ward against this either with continuously checking logic or the torque limiters Animats mentioned: https://www.mayr.com/en/products/torque-limiters If the inception drive is set to low torqu…

How cannot you have a continous checking logic in the driver logic of a gearless drive?

Let me help: you can, and I have taken part in developing one.

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