Vibrating screed

A vibrating screed comprising:

• a screed member;
• a brushless direct-current motor including a rotor and a stator;
• a power switching network coupled between a power source and the brushless direct-current motor;
• an exciter assembly configured to vibrate the screed member in response to receiving torque from the motor via a driveshaft, the exciter assembly comprising
• a first eccentric mass fixed on the driveshaft, and
• a second eccentric mass axially moveable along the driveshaft between a first position and a second position in which the second eccentric mass is closer to the first eccentric mass than in the first position;
• and
• an electronic processor electrically coupled to the motor and the power switching network and configured to
• operate the brushless direct-current motor at a selected speed by providing pulse-width modulated signals to the power switching network, the pulse-width modulated signals having a duty ratio, and
• modify the duty ratio to cause the motor to operate at the selected speed when it is detected that the brushless direct-current motor is operating at a current speed that is different from the selected speed.

A vibrating screed comprising:

• a screed member;
• a brushless direct-current motor including a rotor and a stator;
• a power switching network coupled between a battery pack and the brushless direct-current motor;
• an exciter assembly configured to vibrate the screed member in response to receiving torque from the motor via a driveshaft, the exciter assembly comprising
• a first eccentric mass fixed on the driveshaft, and
• a second eccentric mass axially moveable along the driveshaft between a first position and a second position in which the second eccentric mass is closer to the first eccentric mass than in the first position;
• and
• an electronic processor electrically coupled to the motor and the power switching network and configured to operate and maintain the brushless direct-current motor at a selected speed independent of a state of charge of the battery pack.