Method for operating a regenerative braking system of a vehicle and control unit for a regenerative braking system

A control unit for a regenerative braking system, comprising:

• a blending device with the aid of which a first differential variable with regard to an increased generator braking torque of a generator of the braking system and a second differential variable with regard to a reduced generator braking torque of the generator are receivable, taking at least into account the received first differential variable and a predefined hydraulic efficiency characteristic curve of the braking system, a first setpoint variable with regard to a brake fluid volume to be shifted from at least one brake circuit of the braking system to at least one storage volume of the braking system being establishable, and taking into account the received second differential variable and the predefined hydraulic efficiency characteristic curve, a second setpoint variable with regard to a compensating brake fluid volume to be shifted from the at least one storage volume to the at least one brake circuit being establishable;
• a control unit with the aid of which at least one first control signal corresponding to the first setpoint variable may be output to at least one first component of the at least one brake circuit such that an actual brake fluid volume corresponding to the established first setpoint variable is transferrable from at least one of a brake master cylinder and the at least one brake circuit to the at least one storage volume with the aid of the at least one first component, and with the aid of which at least one second control signal corresponding to the second setpoint variable may be output to at least one of the at least one first component and at least one second component of the at least one brake circuit such that the actual brake fluid volume previously transferred to the at least one storage volume is transferrable at least partially from the at least one storage volume to the at least one brake circuit;
• and
• a characteristic curve establishing device with the aid of which at least one reaction variable with regard to a hydraulic reaction of the braking system to the actual brake fluid volume transferred at least partially from the at least one storage volume to the at least one brake circuit is receivable, and the hydraulic efficiency characteristic curve of the braking system is reestablishable by at least taking into account the at least one ascertained reaction variable with regard to the hydraulic reaction of the braking system to the actual brake fluid volume transferred at least partially from the at least one storage volume to the at least one brake circuit.