Disclosed is an ambulatory infusion device, including a pump drive unit (2), a valve drive unit (1) and a control unit (40). The pump drive unit (2) includes a pump actuator (20) and a pump driver (21) coupled to the pump actuator (20), the pump driver (21) being designed for coupling to a piston (302) of a metering pump unit (30) for transmitting a pump driving force and/or pump driving torque from the pump actuator (20) to the piston (302). The valve drive unit (1) includes a valve actuator (10) and a valve driver (12) coupled to the valve actuator (10), the valve driver (12) being designed for coupling to a valve unit (31) for transmitting a valve switching force and/or valve switching torque from the valve actuator (10) to the valve unit (31).The control unit (40) is configured to control a repeated execution of a sequence of:a) operating the valve actuator (10) to switch the valve unit (31) into a filling state；b) operating the pump actuator (20) to displace the piston (302) in a retraction direction；c) operating the pump actuator (20) to displace the piston (302) into an advancing direction, the advancing direction being opposite to the retraction direction, by an backlash compensation distance；d) operating the valve actuator (10) to switch the valve unit (30) from the filling state into a draining state；e) operating the pump actuator (20) to further displace the piston (302) in the advancing direction in a number of incremental steps over an extended time period.
