Method for controlling continuously variable transmission and continuously variable transmission system

A method for controlling a continuously variable transmission, the method controlling in/out of oil to/from a primary oil chamber by using an oil pump provided in an oil passage between the primary oil chamber and a secondary oil chamber, the method comprising:

• determining whether a required downshift speed is faster than an allowable value;
• setting a target piston position of the primary oil chamber in accordance with an operating state of a vehicle and performing a position control of a piston of the primary oil chamber based on the target piston position;
• setting a target oil pressure of the primary oil chamber in accordance with the operating state and performing a hydraulic control of the primary oil chamber based on the target oil pressure;
• and
• increasing weighting of a position feedback control based on the target piston position in the setting of the target piston position when it is determined that the downshift speed is slower than the allowable value and increasing weighting of a hydraulic feedback control based on the target oil pressure in the setting of the target oil pressure when it is determined that the downshift speed is faster than the allowable value.