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__TOC__
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= Abstract =
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== Abstract ==
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Ardumower uses two different types of motors (all motors can be purchased via the [https://www.marotronics.de/index.php?k=7 shop] [[File: shopping.png|link=https://www.marotronics.de/index.php?k=7]]):
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To control a motor, it requires a 'motor driver' - a circuit that allows current to flow either one direction or the opposite direction through the motor - depending on wether the motor should turn forward or backward (so called 'H-bridge'). There are many motor drivers available as ready-circuit boards, some can even control two motors (Dual H-Bridge) - if you connect two of their H-bridges in parallel, the maximum motor current can be increased.
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* Two motors (with integrated gearing) for driving (wheel motors) and with integrated encoders (for distance and speed control)
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* One motor (with high rotation speed) for mowing (mower motor)
  
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If the direction of the motor does not need to be controlled, (e.g. for the blades), you do not need an H-bridge, but instead a simple 'switch' (e.g. MOSFET-transistor-circuit).
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To control the motors, it requires motor drivers. In addition, the motor driver measures the motor current, and allows us to detect obstacles as motor current increases at obstacles. Ardumower uses two dual MC33926 motor drivers, so two channels for left and right motor and two dual channels (connected in parallel) for the mowing motor.
  
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== Popular modules ==
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It is not safe to connect motors directly to the motor driver. Especially, when quickly turning motors from forward to reverse (or vice verse), high voltage spikes appear, and these could damage the motor drivers in the long run. Therefore, we developed driver protector boards that are connected between motor driver and motor.
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* MC33926, up to 3A with integrated current sensor and thermal shut-down protection (for all kind of robot mowers)
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* STL298N (Arduino L298N motor driver), up to 4A (for Tianchen TC-G158, Ambrogio L50, etc.)
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* STL6203/STL6201PS, up to 4A
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* STL9958 (Arduino 240W H-bridge Motor Driver Board - SX8847), up to 8A (for Rotenbach SPM08-320 etc.)
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== Wheel motors (H-Bridge) ==
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[[File:Ardumower_motordriver_overview.png|800px]]
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The motor driver is connected through control signals to the Arduino. Example:
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Arduino Digital Pin —> MOTOR-DIR Pin
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= Voltages =
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Arduino PWM Pin —> MOTOR-PWM Pin
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As in all modern systems, Ardumower uses 24V motors.
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Arduino Analog Pin <— MOTOR-Current Sensor Pin
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One pin controls the direction (forward/backward), the other pin controls the speed One analog input pin is connected to the current sensor The current sensor module (ACS712-05A) is connected in series with the motor.
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= Motor driver assembly (dual MC33926) =
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Motor driver features: up to 3A with integrated current sensor and thermal shut-down protection
  
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== MC33926 motor driver ==
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<gallery>
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File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
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File: Pcb_mc33926.jpg | PCB and MC33926
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File:Mc33926.jpg | MC33926 pinout
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File:MC33926_schematics.jpg | MC33926 schematics
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</gallery>
  
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== L298N motor driver ==
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* [https://www.youtube.com/watch?feature=player_embedded&v=DokrJiVzX2I Video instructions: Dual MC33926]
  
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== L9958 motor driver ==
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For wiring of motor drivers, protector and motors, please open manual in section Protector PCB.
  
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== Mower motor (MOSFET) ==
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=Protector PCB=
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For a the mowing motor, a MOSFET circuit is used. The MOSFET transistor IRLIZ44N (alternatives: IRF1404, IRL540N, RFP30N06LE, FQP30N06L) can already switch a current of 30A at the Arduino 5V control signal (N-LogL). The 10K resistor pulls down to ground when the Arduino starts. The 180 Ohm resistor limits the current at the Gate caused by level switches to about 30mA. The diode (MBR1045) protects  the circuit against current caused by motor induction. A current sensor module (ACS712-30A) is connected in series with the motor.
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[[File:warning.png]] When quickly tunring motors from forward to backward (or vice versa), high voltage spikes appear. These high voltage spikes could damage the motor driver in the long run. To eliminate high voltage spikes, it is adviced to use a [https://github.com/Ardumower/ardumower/blob/master/Dokumentation/Protector%20Board/WORKSHOP%20Protector-Board.pdf Protector board] between motor driver and motor. Two Protector PCBs are required, one for the gear motors, and one for the mowing motor.
  
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'''Security note: For security reasons, always remove mower blades in your first tests!'''
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<gallery>
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File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
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File:Protector_pcb2.jpg | Protector PCB
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File:Protector_wiring.png | Protector PCB wiring
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File:driver_hw_protection.png | Protector PCB schematics
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</gallery>
  
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== Choosing a driver ==
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* [https://github.com/Ardumower/ardumower/blob/master/Dokumentation/Protector%20Board/WORKSHOP%20Protector-Board.pdf Assembly manual: Protector board (required for safe-use of motor drivers!)]
  
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When purchasing a motor driver, consider...
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= Wheel motors wiring =
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* max. thermal load (short-circuit current)
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<gallery>
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* price
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  File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
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  File: ardumower_motor.jpg | Ardumower gear motor with encoder (8mm diameter, 5900 rpm motor, 0.055 Nm, gear ratio 1/212, output torque 2.45Nm, output rpm 31)
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  File: magnetic_encoder.PNG | Motor wiring
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  File: wheel_motor_diagram.png | Ardumower gear motor curve (motor only)
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  File: Ardumower_gearbox.png | Gearbox specification
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</gallery>
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The two left and right gear motors are controlled independently (aka 'differential driving') to:
  
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== Short-circuit current ==
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* drive the robot forward/backward
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To not damage the motor driver on the first run, find out the maximum current that can flow through your motors. In other words, find out the 'short-circuit' current. Typical measurement installation:
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* steer the robot left/right
  
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Battery === Ampere meter === Motor
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Wheel motor features:
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* A rotation speed up to 31 rpm allows to move the robot at sufficient speed (at up to meter/sec = 31rpm/60 * PI * 0.25m  = 0.4m/sec using 250mm diameter wheels)
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* A high torque (2.45Nm) guarantees that the robot can climb small hills as well (with 2 motors, 0.125 radius wheel, 31rpm = 0.4m/s, acceleration = 0.2 ( 1/2 of nominal speed) [http://www.robotshop.com/blog/en/drive-motor-sizing-tool-9698 see calculator]
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* Integrated encoders, so it can measure the rotation speed and the distance
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* 24V  (load current ~1A)
  
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The Amperemeter (e.g. model making) should be able to measure the maximum current (e.g. 30A). The motor to be measured is mechanically blocked (so it cannot rotate).
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The left gear motor is connected as follows to the protector board:
  
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'''Warning'''
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Motor wiring (left motor):
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Motor (black)  ==== Protector board Motor_1_OUT(1)
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Motor (red)    ==== Protector board Motor_1_OUT(2)
  
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* always remove blades
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For right motor, use Protector board Motor_2_OUT(1,2) accordingly.
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* only connect battery for a short period (1-5 seconds)
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* always use cables with sufficient wire cross section
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Example measurement:
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= Wheel motors odometry wiring =
  
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* Rotenbach SPM08-320
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The Ardumower gear motors have integrated encoders. These encoders help us to compute speed and traveled distance. Here's how you connect the motor odometry wires to the PCB.
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** Wheel motor: 8A
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** Mowing motor:
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* Ambrogio L50
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<gallery>
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** Wheel motor: 4,5A
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  File: magnetic_encoder.PNG | Motor wiring
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** Mowing motor: 22A
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  File: ardumower_odometry_encoder.jpg | Encoder signal
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</gallery>
  
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* Tianchen TC-G158
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Motor odometry wiring (left motor):
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** Wheel motor: 5,4A
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Motor (brown)  ---- PCB VCC
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** Mowing motor: 16A (both 32A)
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Motor (green)  ---- PCB GND
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Motor (blue)  ---- PCB OdometryLeft (3)
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Motor (purple) ---- PCB OdometryLeft (4)
  
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The measured current will only flow in 'worst-case' scenarios, which means when the motor starts or when it is blocked and it will only flow for a short time  (as your battery might not deliver the high current constantly, and so current and voltage will break down).
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For right motor, use PCB OdometryRight accordingly.
  
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IMPORTANT: PCB v0.5/1.2 are missing pull-up resistors! You need to add them yourself at the PCB:
  
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== Current sensor ==
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PCB OdometryLeft(3) --- 4.7k --- 5v
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To detect certain conditions (robot drives against obstacle, motor blocks etc.), the motor current should be monitored constantly. There are two approaches for sensing current.
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PCB OdometryLeft(4) --- 4.7k --- 5v
  
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=== Approach "Hall sensor module" ===
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= Mower motor wiring =
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This is the recommended approach for sensing current. These current sensor modules are available for different current ranges.
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<gallery>
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File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
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File: ardumower_mower_motor.jpg | Ardumower mower motor
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File: Mower_motor_curve.png | Ardumower mower motor curve
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File: Mower2_start_current.png | Mower start current
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File: Mower4_blocked_500ms_detect_5s_wait.png | Mower blocked, 500ms detection (max), waittime: 5sec (min)
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</gallery>
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The Ardumower mower motor features:
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* Fast enough to cut the lawn (3150 rpm)
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* Enough torque (140 mNm / 46 W)
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* Quiet mowing (you cannot hear it)
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* 24V, load current ~1.0A  (L=2.8mH, R=1.9ohm)
  
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* ACS712ELC-05A (185mV/A, max. 5A)
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[[File:warning.png]]'''Security note: For security reasons, always remove mower blades in your first tests!'''
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* ACS712ELC-20A (100mV/A, max. 20A)
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* ACS712ELC-30A (66mV/A, max. 30A)
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* The lower the range, the more precise the measurement.
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=== Approach "Shunt resistor (circuit)" ===
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The current flows across a very small resistor (0.5 Ohm) and the voltage drop is measured
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Here's how you connect the mowing motor to the protector board:
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Motor (black)  ==== Protector board Motor_1_OUT(1)
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Motor (red)    ==== Protector board Motor_1_OUT(2)
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= Motor decrease noise =
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Here's how you can decrease motor noise:
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<gallery>
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  File:decrease_motor_noise.png | Decrease motor noise
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</gallery>
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* [https://github.com/Ardumower/ardumower/blob/master/Dokumentation/Motor%20Entstoerung/Motor%20EntstoerungREV20150531.pdf Instructions: Motor-decrease noise REV20150531]
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* [http://www.ardumower.de/media/kunena/attachments/1725/Motor-EntstoerungREV20150531.pdf (English comments)]
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= Motor controller (PID) =
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The speed of the motors is controlled by a software PID controller. You can monitor the quality of the motor speed control via pfodApp (Plot->Motor control):
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<gallery>
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  File:Speedcontrol.png | Motor speed settings
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  File: Odometry_motor_pid_controller.png
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</gallery>

Aktuelle Version vom 22. Februar 2017, 09:45 Uhr

Abstract

Ardumower uses two different types of motors (all motors can be purchased via the shop Shopping.png):

  • Two motors (with integrated gearing) for driving (wheel motors) and with integrated encoders (for distance and speed control)
  • One motor (with high rotation speed) for mowing (mower motor)

To control the motors, it requires motor drivers. In addition, the motor driver measures the motor current, and allows us to detect obstacles as motor current increases at obstacles. Ardumower uses two dual MC33926 motor drivers, so two channels for left and right motor and two dual channels (connected in parallel) for the mowing motor.

It is not safe to connect motors directly to the motor driver. Especially, when quickly turning motors from forward to reverse (or vice verse), high voltage spikes appear, and these could damage the motor drivers in the long run. Therefore, we developed driver protector boards that are connected between motor driver and motor.

Ardumower motordriver overview.png

Voltages

As in all modern systems, Ardumower uses 24V motors.

Motor driver assembly (dual MC33926)

Motor driver features: up to 3A with integrated current sensor and thermal shut-down protection

  • PCB, MC33926, protector and motors

  • PCB and MC33926

  • MC33926 pinout

  • MC33926 schematics

For wiring of motor drivers, protector and motors, please open manual in section Protector PCB.

Protector PCB

Warning.png When quickly tunring motors from forward to backward (or vice versa), high voltage spikes appear. These high voltage spikes could damage the motor driver in the long run. To eliminate high voltage spikes, it is adviced to use a Protector board between motor driver and motor. Two Protector PCBs are required, one for the gear motors, and one for the mowing motor.

  • PCB, MC33926, protector and motors

  • Protector PCB

  • Protector PCB wiring

  • Protector PCB schematics

Wheel motors wiring

  • PCB, MC33926, protector and motors

  • Ardumower gear motor with encoder (8mm diameter, 5900 rpm motor, 0.055 Nm, gear ratio 1/212, output torque 2.45Nm, output rpm 31)

  • Motor wiring

  • Ardumower gear motor curve (motor only)

  • Gearbox specification

The two left and right gear motors are controlled independently (aka 'differential driving') to:

  • drive the robot forward/backward
  • steer the robot left/right

Wheel motor features:

  • A rotation speed up to 31 rpm allows to move the robot at sufficient speed (at up to meter/sec = 31rpm/60 * PI * 0.25m = 0.4m/sec using 250mm diameter wheels)
  • A high torque (2.45Nm) guarantees that the robot can climb small hills as well (with 2 motors, 0.125 radius wheel, 31rpm = 0.4m/s, acceleration = 0.2 ( 1/2 of nominal speed) see calculator
  • Integrated encoders, so it can measure the rotation speed and the distance
  • 24V (load current ~1A)

The left gear motor is connected as follows to the protector board:

Motor wiring (left motor): 

Motor (black)  ==== Protector board Motor_1_OUT(1)
Motor (red)    ==== Protector board Motor_1_OUT(2)

For right motor, use Protector board Motor_2_OUT(1,2) accordingly.

Wheel motors odometry wiring

The Ardumower gear motors have integrated encoders. These encoders help us to compute speed and traveled distance. Here's how you connect the motor odometry wires to the PCB.

  • Motor wiring

  • Encoder signal

Motor odometry wiring (left motor): 

Motor (brown)  ---- PCB VCC
Motor (green)  ---- PCB GND
Motor (blue)   ---- PCB OdometryLeft (3)
Motor (purple) ---- PCB OdometryLeft (4)

For right motor, use PCB OdometryRight accordingly.

IMPORTANT: PCB v0.5/1.2 are missing pull-up resistors! You need to add them yourself at the PCB: 

PCB OdometryLeft(3) --- 4.7k --- 5v
PCB OdometryLeft(4) --- 4.7k --- 5v

Mower motor wiring

  • PCB, MC33926, protector and motors

  • Ardumower mower motor

  • Ardumower mower motor curve

  • Mower start current

  • Mower blocked, 500ms detection (max), waittime: 5sec (min)

The Ardumower mower motor features:

  • Fast enough to cut the lawn (3150 rpm)
  • Enough torque (140 mNm / 46 W)
  • Quiet mowing (you cannot hear it)
  • 24V, load current ~1.0A (L=2.8mH, R=1.9ohm)

Warning.pngSecurity note: For security reasons, always remove mower blades in your first tests!


Here's how you connect the mowing motor to the protector board: 

Motor (black)  ==== Protector board Motor_1_OUT(1)
Motor (red)    ==== Protector board Motor_1_OUT(2)

Motor decrease noise

Here's how you can decrease motor noise:

  • Decrease motor noise


Motor controller (PID)

The speed of the motors is controlled by a software PID controller. You can monitor the quality of the motor speed control via pfodApp (Plot->Motor control):

  • Motor speed settings

  • Odometry motor pid controller.png
Von „https://wiki.ardumower.de/index.php?title=Motor_driver&oldid=4333“