#robotics Logs

Jan 12 2022

05:02 AM Tom_itx is now known as Tom_L
09:25 AM rue_mohr: my bigtrak software is looking good, hoping to install it on one of the platoforms later today
12:55 PM -!- #robotics mode set to +o by strontium.libera.chat
04:51 PM machinehum: Is there a name for a joint like this? https://i.imgur.com/hNWNO6c.png
04:51 PM machinehum: It's a rotary joint created from a ball screw connected to a rod, where the other end is connected to the other bar
04:52 PM machinehum: I don't know if that made sense
04:52 PM machinehum: Could be used for a foot, knee, whatever
04:52 PM machinehum: This would give you finer control over the torque by changing the pitch of the ball screw
04:53 PM machinehum: and the length of that rod
05:17 PM Tom_L: not sure what you're asking but i'm thinking heim joint
05:18 PM Tom_L: https://www.amazon.com/Heim-Joints/s?k=Heim+Joints
05:20 PM machinehum: I would have to CAD it out
05:20 PM machinehum: I guess that picture made no sense
05:20 PM machinehum: Thanks though
05:20 PM Tom_L: you would have to mount the joint to a block on the screw
05:22 PM machinehum: Tom_L: Yeah that's the idea, and for that I can use something like the heim joint
05:37 PM Tom_L: what's it for?
05:38 PM Tom_L: all the torque would be in the middle of the screw
05:38 PM Tom_L: as you approach the end, the angle of the rod would decrease the torque
05:38 PM Tom_L: alternate: a stationary hydraulic cylinder
05:39 PM machinehum: Tom_L: Just a rotary joint I've though of
05:39 PM machinehum: It would replace a motor on the joint directly with a gearbox
05:39 PM Tom_L: scissor lift
05:39 PM machinehum: Yeah I guess the rotary torque would be non constant
05:40 PM machinehum: Yeah so this would be a cheaper version of a stationary hydraulic cylinder
05:41 PM machinehum: Small electric motor, lead screw you can vary the pitch of to change the torque, you can change the mounting point of the fixed end
05:41 PM machinehum: To change the travel
05:41 PM Tom_L: but if you mounted the screw on the side and used the block attached to the other piece the torque would be more constant
05:41 PM Tom_L: both in a stationary fixed point
05:42 PM machinehum: You mean eliminate the rod? And just have the screw connecting the two
05:43 PM Tom_L: yup
05:43 PM machinehum: One problem with that is there's then a leadscrew sticking out the back of the robots calf
05:43 PM Tom_L: it may end up being in the way
05:43 PM machinehum: Yeah
05:44 PM Tom_L: so use your first idea but put a cable on the block and take it around a pulley _almost_ at the joint but not quite and attach the cable to the other half
05:45 PM Tom_L: so the cable would slide linear to the pulley and you would have a fixed point at the pulley
05:45 PM Tom_L: giving you even torque
05:45 PM Tom_L: i think
05:45 PM Tom_L: the angle would still mess with that though
05:52 PM machinehum: Even with the nonconstant torque I think it's a decent mechanism for a walking robot
05:53 PM machinehum: I'm not following the cable idea
05:53 PM Tom_L: it's no better so don't try :)
05:53 PM machinehum: lol