Nummer4 Realtime Distributed Calculation
From Sven Kreiss
The new electronic design for Nummer4punkt2 includes the distribution of mathematical methods to different controllers. At this stage most important is the calculation of the angles from the space coordinates of a foot. This should be done by the master controller on the board for the leg. The problem is that the „brain“ does not get any information about the exact angles before the leg has done it. But it would be better at all if these information do not have to be transmitted at all. The „brain“ needs these information to do the inverse kinematics for the arms. So normally the brain has to know the exact angles and the motion of the masses in the leg to calculate the motion of the arms in that way that the ZMP Criterion is fulfilled.
Highspeed calculation and transmission would minimize the problem to a not noticeable minimum. The controller would get a new position before the slightly false old ones take any effect. The delay would always be one cycle.
As an approximation it might be possible to take the position of the foot as a reference. If the knee gets bend the mass distribution is slightly in front of the line between foot and hip. If we calculate the equivalent postion for the arms just from the space coordinates and prefer the position when the elbow goes straight backwards, the mass distribution of the arm should be slightly behind the line between hand and shoulder. Hopefully this two errors cancel each other. This should also hold for the derivatives, the speed and the acceleration of the angles.
SHOULD BE TESTED ON REAL MODEL!
The consequences of this model should be that no one else than the leg controllers do need the exact position of the motors. With this method the „brain“-controller just needs the space coordinates which it calculates itself.