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### Select BLDC motor for AGV

Posted: **Mon Jun 12, 2017 1:40 am**

by **cokthemhok**

Hi OM tech support,

I have the project about AGV (Automated guided vehicle), which heavy load and high speed.

I try to find out suitable BLDC motor but I cannot. Could you help me?

Request specification:

- Load: 700kg

- Speed: 1m/s

- AGV type: Pull type

- 2 motor driven

I calculated permissible load inertia, but it is too big.

If there isn't any suitable motor, how maximum speed I can use?

Thanks for your support.

### Re: Select BLDC motor for AGV

Posted: **Mon Jun 12, 2017 1:02 pm**

by **om_tech_support_JS**

Hi cokthemhok,

What value did you calculate for the load inertia? In order to select a motor, the **speed**, **torque**, and **inertia **values will all be required. In order to determine these values, a sizing will need to be completed to calculate for these values. If you would like, we can size this application for you and then provide a motor option; with the exception that we offer a product that meets your requirements.

In order to complete the sizing, I will need to know the diameter of the AGV wheels. Will the motor be directly driving the wheel, or will there be a pulley or gear system? If there is a mechanical system, then I would require those dimensions and weights as well.

### Re: Select BLDC motor for AGV

Posted: **Mon Jun 12, 2017 6:51 pm**

by **cokthemhok**

Hi OM tech support,

This is my calculation:

- AGV mass: ~100kg

- Load: 700kg

- Wheel mass: ~1kg

- Wheel diameter: 0.2m

- Speed: 1m/s

=>Gear shaft speed: (60*1)/(Pi*0.2)=95.5 (rpm)

=> Select gear ratio = 30 (Speed range: 3.3~133 rpm) (I use BLV series)

Inertia of AGV and load: (100+700)*((Pi*0.2)/(2*Pi))^2=8(kg.m^2)

Inertia of wheel: 1/8*(1*0.2^2)=0.05

Total inertia: 8+2*0.05=8.1 kg.m^2

For 1 motor: 8.1/2 = 4.05 = 40500 *10^-4 kg.m^2

=> There isn't any motor with permissible load inertia more than 40500 *10^-4 (Gear ratio is 30)

The motor driving the wheel by chain driven with ratio 1:1. But I can change it if necessary.

Is my calculation correct?

Could you support me to select suitable motor?

Thank you for your support.

### Re: Select BLDC motor for AGV

Posted: **Tue Jun 13, 2017 1:03 pm**

by **om_tech_support_JS**

Hi cokthemhok,

Your calculations look good, however, there seems to be an error with your inertia of the wheel. This value should come out to **0.005** instead of 0.05. Taking into account the inertia of the AGV and load is what is the most important, this change in the value has no drastic affect on the total inertia.

Another important calculation is the Torque calculation. The torque will be split up between the acceleration torque and the load torque. For the load torque, the torque would be equal to the (Force x wheel diameter) / (2 x efficiency of the system). The Force would be determined by the total mass (800kg) x gravity (9.81m/s^2) x coefficient of friction between the wheel and the ground.

However, as you previously stated, the single motor inertia of 8.01/2 = 4.005 = 40050 *10^-4 kg.m^2 is larger than our BLV product offers. The 400 Watt BLV motor is the largest DC input voltage speed control motor option that we offer. The largest gear ratio for this motor is 200:1. This system would then offer a permissible inertia of 37000 × 10-4 kg·m². Since this motor is unable to meet the inertia requirements, we are unfortunately unable to recommend a motor for your application. Furthermore, adding any additional gearing would decrease the speed of the AGV as well as affect the system efficiency.

### Re: Select BLDC motor for AGV

Posted: **Tue Jun 13, 2017 7:08 pm**

by **cokthemhok**

Hi OM Tech support,

Thank you so much for your answers.

I will find other solution for my application.