Blog 6

 Introduction

This blog mainly discusses the research on the swarm robot, resolving the issue mentioned in the previous blog where the motor controller failed to start, and the problem of the tires not turning after the relevant cables were successfully connected.

 About motor controller connection

To detect the error, we reviewed the data sheet again and checked the connections, voltages, and waveforms of each pin on the oscilloscope.

We first checked the voltage at the GND:

The voltage reading was 0, which is correct.

We then checked the VCC connector and found that the voltage was lower than required

(5V Switching BEC).

 After checking the power supply, we discovered that it was not fully charged, only providing 4V. Realizing the problem, we replaced the battery with a new one  (12.09V).

And check the voltage of the switch again.

 

According to the results from the multimeter and oscilloscope, the voltage has finally returned to normal.

Next, we checked the PWM signals to ensure that the motor controller was receiving them.

(According to Jason's code: 100 forward 150 stop 200 backward )

S1 PMW :150 stop

S2 PMW :150 stop

Strangely, even after we ensured that all the wiring was correct and the PWM signal was correct, the tire still wouldn't turn. Team members suggested checking the buttons on the controller to see if they could control the tire's rotation.

Motor controller state

Initially, the DIP switches were set incorrectly due to ignorance of the button and the state, which resulted in the motor driver not responding correctly to control inputs. 

After revisiting the user guide, the DIP switches were set to:

$$\mathbf{\text{DOWN}}\mathbf{\text{UP}}\mathbf{\text{UP}}\mathbf{\text{DOWN}}\mathbf{\text{UP}}\mathbf{\text{DOWN}}\mathbf{\text{<br>}}$$

In this configuration, each switch performs a specific function:

• Switch 1 (DOWN): Selects the input mode. Setting it to DOWN enables a serial control mode, which matches the microcontroller-based communication used in the system.
• Switch 2 (UP): Defines part of the operating mode selection. In combination with other switches, this enables the correct serial communication mode.
• Switch 3 (UP): Works with Switch 2 to determine addressing and command format, ensuring that the Sabertooth interprets incoming data correctly.
• Switch 4 (DOWN): Controls response characteristics such as mixing or exponential control. Setting it to DOWN provides a linear and predictable motor response, improving control stability.
• Switch 5 (UP): Configures features such as battery protection or communication parameters (depending on mode). Setting it to UP ensures compatibility with the system setup.
• Switch 6 (DOWN): Determines baud rate or packet handling behaviour. Setting it to DOWN aligns the communication speed with the microcontroller, allowing correct decoding of serial data.

THANKS TO TEAMATES, THE SWORM ROBOT'S TIRES FINALLY STARTED TURNING!!!!!!

Results after the configuration

Here is the video of the sworm robot:

It is teamwork that contributes to the success!