System and a method for the control of variable-ratio transmissions

A system for controlling a variable-ratio transmission mounted on an apparatus (1), the transmission being associated with:

• an actuator (2) for changing the transmission ratio, and
• operating means (3) for applying an input driving force to the transmission by a periodic action of given frequency,
• the system comprising:
• the first sensor means (5) which are sensitive to the driving force and can generate a respective first signal,
• second sensor means (6) which are sensitive to the speed of operation of the apparatus (1) and can generate a respective second signal, and
• a control device (4) which is sensitive to the first signal and to the second signal and which can control the actuator (2) in dependence on the first signal and the second signal,
• and the system including that:
• third sensor means (7) which are sensitive to the given frequency and which can generate a respective third signal are provided,
• the control device (4) is configured to determine, from at least the first signal and the second signal, a reference signal indicative of a reference value for the frequency (CR),
• the control device(4) can compare (42, 108) the reference signal and the third signal so as to identify a corresponding deviation signal (e), and
• the control device (4) is configured to act on the actuator (2), changing the transmission ratio so as to minimize the deviation signal (e).