Infusion pumps

A method of operating an infusion apparatus including a barrel defining a medicament reservoir, a plunger with at least one seal in the barrel such that there is static and dynamic friction between the barrel and the plunger, a plunger pusher and a motor that drives the plunger pusher by providing motor torque, the method comprising the steps of:

• when using the motor to propel the plunger pusher to drive the plunger, controlling the motor torque such that the motor torque is continuously within a range having a lower limit torque that is sufficient to overcome a cartridge break force and a running force to move the plunger and an upper limit torque that is low enough so as to not cause leakage past the at least one seal of the plunger due to excessive pressure in the reservoir by
• exciting the motor at an excitation current such that motor will generate the lower limit torque to propel the pusher,
• monitoring motor rotation while the motor is being excited, and
• in response to a lack of rotation of the excited motor, repeating the exciting step at an up-regulated excitation current so as to increase the motor torque from the lower limit torque to an increased motor torque that is below the upper limit.