# Gains and limits

The commands that set the loop gains and the limits. None of them is answered; save with Send_Save_config.

### Send_PD_Gains

<div class="cmd-facts" markdown><span class="fact">ID 16</span><span class="fact">host → driver</span><span class="fact">8 bytes</span><span class="fact">Python: `Send_PD_Gains()`</span></div>

Sets KP and KD, the gains of the impedance (PD) loop. Keep them with Send_Save_config.

**8 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | KP | float 32 |  |
| 4-7 | KD | float 32 |  |

</div>

The driver does not answer this command.

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### Send_Current_Gains

<div class="cmd-facts" markdown><span class="fact">ID 17</span><span class="fact">host → driver</span><span class="fact">8 bytes</span><span class="fact">Python: `Send_Current_Gains()`</span></div>

Sets Kp and Ki of the PI current loop of Iq. The Id loop keeps its gains; over UART, `#Kpiq` and `#Kiiq` set both loops, and so do parameters 11 and 12, a calibration and parameter 49.

**8 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | Kp_iq | float 32 |  |
| 4-7 | Ki_iq | float 32 |  |

</div>

The driver does not answer this command.

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### Send_Velocity_Gains

<div class="cmd-facts" markdown><span class="fact">ID 18</span><span class="fact">host → driver</span><span class="fact">8 bytes</span><span class="fact">Python: `Send_Velocity_Gains()`</span></div>

Sets Kp and Ki of the PI velocity loop.

**8 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | Kpv | float 32 |  |
| 4-7 | Kiv | float 32 |  |

</div>

The driver does not answer this command.

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### Send_Position_Gains

<div class="cmd-facts" markdown><span class="fact">ID 19</span><span class="fact">host → driver</span><span class="fact">4 bytes</span><span class="fact">Python: `Send_Position_Gains()`</span></div>

Sets Kp of the P position loop.

**4 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | Kpp | float 32 |  |

</div>

The driver does not answer this command.

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### Send_Limits

<div class="cmd-facts" markdown><span class="fact">ID 20</span><span class="fact">host → driver</span><span class="fact">8 bytes</span><span class="fact">Python: `Send_Limits()`</span></div>

Sets the speed limit and the current limit the loops may reach. From firmware 109 the current limit stops at the driver's maximum of 2800 mA, as `#Ilim` does, and a negative value or one that is not a number is ignored. Firmware 108 and older stored the limit as sent. Send no more than the motor's rated current.

**8 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | Speed limit | float 32 | encoder ticks/s |
| 4-7 | Current limit | float 32 | mA |

</div>

The driver does not answer this command.

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### Send_Kt

<div class="cmd-facts" markdown><span class="fact">ID 22</span><span class="fact">host → driver</span><span class="fact">4 bytes</span><span class="fact">Python: `Send_Kt()`</span></div>

Sets the motor's torque constant Kt, which the driver uses to estimate torque from current.

**4 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | Kt | float 32 | Nm/A |

</div>

The driver does not answer this command.

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### Send_Voltage_Limit

<div class="cmd-facts" markdown><span class="fact">ID 34</span><span class="fact">host → driver</span><span class="fact">4 bytes</span><span class="fact">Python: `Send_Voltage_Limit()`</span></div>

Sets the voltage limit of the current loops (the same value as `#Vlim`), in mV. 0 means use the supply voltage. Added in firmware 105. From firmware 109 it takes 0 to 60000 mV, as parameter 17 does; a value outside is ignored.

**4 bytes**

<div class="ref-table fields" markdown>

| Byte | Field | Type | Meaning |
|---|---|---|---|
| 0-3 | Voltage limit | signed 32-bit | mV; 0 = Vbus |

</div>

The driver does not answer this command.

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