US Patent 8988015 Power tool having a non-linear trigger-speed profile

A power tool including a motor, an input unit such as a variable-speed trigger switch, and a controller is provided. The controller controls the speed of the motor as a function of the input level indicated by the electrical signal from the input unit. The function is a first expression within a first predetermined range of the input level and a second expression within a second predetermined range of the input level, where the second expression corresponds to a polynomial of a second degree or higher and is different from the first expression.