incorrect force measurement

[ShenC]

Hi,

I am doing a simulation with Simulink (with sampling time 1ms) and Adams.
This simulation is about a quadruped robot running on the flat ground with rolling foot, like Rhex robot.
This model is about 10kg and runs under 1 to 1.5m/s in the simulation.
The variation of potential energy is minimized, because the body of the model is moving parallel to the flat ground.
However, when I try to measure the normal force from the ground. The total force summed from four legs is much less than its weight, which should be roughly equal to its weight. This situation becomes worse, if the robot running in higher speed.
I might set something incorrect, and I'll appreciate it, if I can get any help about this.

 

[GregLocock]

I suggest you use the database navigator and make sure you have measured all the forces in all the pathways between each foot and the ground, and that you have only one ground.

Cheers

Greg Locock


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[ShenC]

Thanks for your reply.
I found that the circles(step file) I imported, which roll on the ground during the simulation, are not considered as circles.
So I used the cylinders directly in the adams instead. The situation has been improved a lot, but the normal force still reduces when the running speed increases.
I guess the reason might be the calculation of the contact force.

 

[GregLocock]

I think you still must be doing something wrong, if there is a net downwad force then the object will accelerate downwards.

Cheers

Greg Locock


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