Patent ID: 11870384
Assignee: HITACHI INDUSTRIAL EQUIPMENT SYSTEMS CO., LTD.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC G  H | IPC H

Claim 0:
1. A speed calculation device that calculates a speed of an object to be driven from output pulses obtained from an encoder connected to the object to be driven,
wherein a duty ratio of a time of a half cycle from a rising edge to a falling edge of the output pulses to a time of a full cycle between rising edges of the output pulses is measured based on a motor speed instruction,
wherein the speed calculation device outputs a duty measurement-in-progress signal while the duty ratio is being measured, and the motor speed instruction is fixed to a most recently determined value while the duty measurement-in-progress signal is being outputted,
wherein the speed is calculated using the half cycles of the output pulses if the duty ratio is within a prescribed range, and
wherein the speed is calculated using the full cycles of the output pulses if the duty ratio is outside of the prescribed range.