# to much torque robotic arm

Discussion in 'General Electronics Discussion' started by moh, Dec 7, 2009.

1. ### moh

1
0
Dec 7, 2009
Hi,

I was trying to calculate the torque for my robotic arm from societyofrobots website calculator

Here is the spec

motor Hitec ,Torque 10 kg/cm

L1 (Length from shoulder to elbow) 7 inches weight W1 steel frame about 5 g
L2 (Length from elbow to wrist) 5 inches weight W2 steel frame about 4 g
L3 (Length from elbow to gripper) 3 inches weight W3 steel frame about 2 g

W4 object to lift 1kg

M1 (Shoulder 1 motor ) 25g
M2 (Elbow 2 motors) 50g
M3 (gripper 2 motors) 50g

I want to lift 1kg object

I left the Joint Rotational Acceleration blank 0

It is showing about 40kg/cm torque ,Is it correct?

If it is true ,is there any way around it?.

I am using arduino board

2. ### Resqueline

2,848
2
Jul 31, 2009
Using metrics instead of inches makes it much easier to assay the calculation:
(7+5+3)*2.54=15*2.54=38.1cm
Add the small weight of the motors & arms and you get 40kg*cm of torque trying to lift1kg on a straight arm.

One way around it is to lift it like you would lift a heavy object yourself; keep shoulder to elbow frame straight down:
(5+3)*2.54=8*2.54=20.3cm - for the two elbow motors.
That'll tax the motors, but if you add a spring from shoulder to wrist it can double their lifting capacity.