MELSERVO-J4

Direct Drive Motors

Direct Drive Motor Sizing Example 1. Selection criteria (1) Configurations

D T

Table mass

W D T

= 19 kg

Rotation table diameter Rotation angle per cycle

= 300 mm = 270 deg

q t 0

Positioning time = Within 0.45 s Acceleration/deceleration time t p = t psa = t psd = 0.125 s Operating cycle t f = 2.0 s Load torque T L = 0 N•m

Direct drive motor (DD motor)

(2) Direct drive motor speed N 0 = q × 60 360 (t 0 - t p - t s )

(4) Acceleration/deceleration torque Torque required during acceleration T Ma = (J L + J M ) × N 0 = 38.3 N•m 9.55 × t psa

60

= 200 r/min

= 270 × 360

(0.45 - 0.125 - 0.1) t s : settling time. Here assumed 0.1 s.

J M : moment of inertia of DD motor

Torque required during deceleration T Md = - (J L + J M ) × N 0 = -38.3 N•m 9.55 × t psd Torque required during acceleration/deceleration must be equal to or lower than the max. torque of the DD motor.

(3) Operating pattern

Speed [r/min]

200

(5) Continuous effective load torque T rms = T

0

Time [s]

Ma 2 × t psa + T L 2 × t c + T Md 2 × t psd

0.1

0.125 t psa

0.125 t psd

= 13.5 N•m

t f t c = t 0 - t s - t psa - t psd Continuous effective load torque must be equal to or lower than the rated torque of the DD motor.

t S

t 0 0.45

1 cycle

t f 2.0

2. Selecting direct drive motor (1) Moment of inertia of load J L = 1 × D T 2 8 × W

(6) Torque pattern

Torque [ N• m]

= 1 × (300 × 10 -3 ) 2 × 19 = 0.214 kg•m 2 8 (2) Torque required to accelerate/decelerate load T a = J L × ( 2 p × N 0 ) ÷ t p 60 = J L × N 0 60 × t p 2 p = 0.214 × 200 9.55 × 0.125 = 35.9 N•m (3) Select a direct drive motor Selection criteria

38.3

0

Time [s]

0.125

0.1 0.125 0.1

-38.3

2.0

(7) Result

Select the following: Direct drive motor: TM-RFM018E20 Servo amplifier: MR-J4-100B

Load torque during accel./decel. , Max. torque of DD motor Moment of inertia of load , J R × Moment of inertia of DD motor J R : Recommended load to motor inertia ratio Select the following direct drive motor to meet the criteria above. TM-RFM018E20 (rated torque: 18 N•m, max. torque: 54 N•m, moment of inertia: 149 × 10 -4 kg•m 2 )

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