# Initialization - Zero reference

The `Calibration Sequence`

can be started by triggering the safety event `doCalibrating`

. This can be done by pressing the red button until this lights up. Press and hold the red button for 2 seconds, this will trigger the Safety Event `doCalibrating`

. When finished with calibrating, press the red button once again. Press the green button to get back in normal operation mode.

### Mechanical Limits of the Axis Motors - Upper limit

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Upper limit calculation shown below | Upper limit calculation detail |

L = 17.5

B = 15

s = 4

The upper limit can be calculated as follows:

*(1) tan(β) = sin(β)/cos(β) = (B-y)/L*

*(2) cos(β) = s/y*

Substitute (2) into (1) to get:

*(3) L*sin(β)-B*cos(β)=-s*

Using following trigonometric formulas in (3):

*(4) t = tan(β/2) *

*(5) sin(β) = 2*tan(β/2)/(1+tan^2(β/2) *

*(6) sin(β) = (1-tan^2(β/2)/(1+tan^2(β/2) *

Leads to:

*(7) (s+B)*t^2 + 2*L*t + (s-B) = 0*

Solutions are:

* t1 = 0.2736 → β = 30.6°*

* t2 = -2.1157 (neg. solution)*

Hence, the maximum angle the axis can turn is * 90° + β ≅ 120°*.

### Mechanical Limits of the Axis Motors - Lower limit

Lower limit of the Axis Motor measured on the Delta robot, γ is about 5°.

The TCP rotation is also limited by two metall pins. The maximum turn angle is calculated as follows:

*sin(γ/2) = r/R*

*γ=2*arcsin(r/R)= 0.0600 (rad) = 3.438°*

That is the value for one side. The other side is identical, so the maximum turn angle is

*β = 2*PI - 2 * 0.06 = 6.16 (rad) ≅ 353°*.