Technogym EXCITE+ VARIO Technical Service Manual page 59

EXCITE + - VARIO: Technical service guide- Ver. 2.1
The braking force imparted by the machine during exercise is a combination of the resistance
produced by the two brakes. Whereas the magnetic brake always opposes a constant predefined
resistance, the resistance of the electromagnetic brake instead depends on the exercise intensity
entered by the user on the display. The display board communicates, via the RS-485 serial link, the
required value of "electrical" power to the brake interface board. On the basis of the commands
received and the feedback signal from the speed sensor, the brake interface board then applies the
appropriate excitation current to the electromagnetic brake winding, which generates an
electromagnetic field.
The value of the current applied is based on the value of the brake table memorized
into the Brake Board.
When the brake interface board receives the signal to generate resistance, the green
LED illuminates.
The electromagnetic field produced by the winding and the rotation of the disk will induce eddy
currents in the disk itself, giving rise to a force that tends to brake its motion. This generates the
exercise resistance.
A higher brake excitation signal will produce a correspondingly higher exercise resistance. In
addition, for a given value of brake excitation, a higher speed of disk rotation will produce a
correspondingly higher exercise resistance.
For the presence of eddy currents, on the brake disc is dissipated energy into heat.
The control on the CURRENT is of type CLOSED LOOP. The Brake Board
calculates the current value to send on the winding of the brake, it controls the supply
with a special driver circuit, and finally checks the actual presence on the brake
circuit through reading and A/D conversion of current signal read.
Control over the Resistance actually present on the pedals (effective user torque) is
Open Loop. The system (Brake Board) + (brake) provides no adjustment to calibrate
the resistance value produced, but only using the braking table stored in the Brake
Board. The accuracy of the braking system has a tolerance of ± 10%.
During the movement, the speed sensor detects the heads of the brake disk fixing screws, and
produces a speed feedback signal that is sent to the Brake board. The brake board will adjust s the
excitation current of the brake winding so that the speed detected by the speed sensor is equal to the
set value.
If the brake board does not receive a speed signal, which indicates that an exercise
session is in progress, the machine will not produce any resistance.
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