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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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== Wheel motors (H-Bridge) ==
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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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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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[[File:Ardumower_motordriver_overview.png|800px]]
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Arduino PWM Pin —> MOTOR-PWM Pin
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Arduino Analog Pin <— MOTOR-Current Sensor Pin
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= Voltages =
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As in all modern systems, Ardumower uses 24V motors.
  
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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
  
 
<gallery>
 
<gallery>
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File:Ardumower_motor_driver_circuit.png
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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
 
</gallery>
 
</gallery>
  
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== Popular modules ==
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* [https://www.youtube.com/watch?feature=player_embedded&v=DokrJiVzX2I Video instructions: Dual MC33926]
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=== MC33926 ===
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Features: up to 3A with integrated current sensor and thermal shut-down protection, for all kind of robot mowers)
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For wiring of motor drivers, protector and motors, please open manual in section Protector PCB.
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=Protector PCB=
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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.
  
 
<gallery>
 
<gallery>
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File:Mc33926.jpg
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File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
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File:Mc33926_example.jpg
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File:Protector_pcb2.jpg | Protector PCB
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File:MC33926_schematics.jpg
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File:Protector_wiring.png | Protector PCB wiring
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File:driver_hw_protection.png | Protector PCB schematics
 
</gallery>
 
</gallery>
  
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M1_FB    --- Motor1 current sensor output (Arduino)
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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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M1_PWM_D1 --- connect with jumper to GND
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M1_PWM_D2 --- connect with jumper to VDD
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M1_IN1    --- Motor1 PWM (Arduino)
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M1_IN2    --- Motor1 Dir (Arduino)
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EN        --- connect with jumper to VDD
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M2_FB    --- Motor2 current sensor output (Arduino)
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M2_PWM_D1 --- connect with jumper to GND
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M2_PWM_D2 --- connect with jumper to VDD
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M2_IN1    --- Motor2 PWM (Arduino)
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M2_IN2    --- Motor2 Dir (Arduino)
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EN        --- connect with jumper to VDD
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VDD      --- Arduino 5V
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=== L298N ===
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Features: up to 4A (for Tianchen TC-G158, Ambrogio L50, etc.)
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Notice: When using a L298N-motor driver, both H-bridges (2A) should be connected in parallel, so that both bridges drive a single motor (max. 4A):
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Connect in parallel:
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IN1 with IN4
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IN2 with IN3
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OUT1 with OUT4
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OUT2 with OUT3
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(Do NOT disconnect the SENSE-lines, except when you want to measure current by a 'shunt' resistor).
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Make sure there is a jumper on both ENA and ENB. Also, make sure there is a jumper on S1.
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= Wheel motors wiring =
 
<gallery>
 
<gallery>
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File: Motordriver_l298n.JPG
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  File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
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File: L298driver.jpg
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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: L298N_schematics.jpg
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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
 
</gallery>
 
</gallery>
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The two left and right gear motors are controlled independently (aka 'differential driving') to:
  
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=== L9958 ===
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* drive the robot forward/backward
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Features: Arduino 240W H-bridge Motor Driver Board - SX8847, up to 8A (for Rotenbach SPM08-320 etc.)
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* steer the robot left/right
  
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L9958 GND---GND
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Wheel motor features:
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  L9958 VCC---Arduino 5V
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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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L9958 EN---Arduino 5V
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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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L9958 DI---GND
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* Integrated encoders, so it can measure the rotation speed and the distance
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L9958 DIR---Arduino MOTOR_DIR
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* 24V (load current ~1A)
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L9958 PWM---Arduino MOTOR_PWM
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L9958 MOTOR(+)---motor(+)
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L9958 MOTOR(-)---motor(-)
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L9958 POWER(+)---battery(+)
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  L9958 POWER(-)---battery(-)
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<gallery>
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The left gear motor is connected as follows to the protector board:
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File: Motor_driver_L9958.jpg
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</gallery>
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== Mower motor (MOSFET) ==
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Motor wiring (left motor):
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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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Motor (black) ==== Protector board Motor_1_OUT(1)
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Motor (red)   ==== Protector board Motor_1_OUT(2)
  
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'''Security note: For security reasons, always remove mower blades in your first tests!'''
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For right motor, use Protector board Motor_2_OUT(1,2) accordingly.
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= Wheel motors odometry wiring =
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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.
  
 
<gallery>
 
<gallery>
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File: Ardumower_mower_motor_circuit.png
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  File: magnetic_encoder.PNG | Motor wiring
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  File: ardumower_odometry_encoder.jpg | Encoder signal
 
</gallery>
 
</gallery>
  
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== Choosing a driver ==
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Motor odometry wiring (left motor):
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Motor (brown)  ---- PCB VCC
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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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When purchasing a motor driver, consider...
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For right motor, use PCB OdometryRight accordingly.
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* max. thermal load (short-circuit current)
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* price
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== Short-circuit current ==
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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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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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Battery === Ampere meter === Motor
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PCB OdometryLeft(3) --- 4.7k --- 5v
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PCB OdometryLeft(4) --- 4.7k --- 5v
  
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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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= Mower motor wiring =
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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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'''Warning'''
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[[File:warning.png]]'''Security note: For security reasons, always remove mower blades in your first tests!'''
  
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* always remove blades
 
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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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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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* Rotenbach SPM08-320
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= Motor decrease noise =
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** Wheel motor: 8A
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** Mowing motor:
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* Ambrogio L50
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Here's how you can decrease motor noise:
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** Wheel motor: 4,5A
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** Mowing motor: 22A
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* Tianchen TC-G158
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<gallery>
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** Wheel motor: 5,4A
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  File:decrease_motor_noise.png | Decrease motor noise
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** Mowing motor: 16A (both 32A)
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</gallery>
  
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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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* [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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== Current sensor ==
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= Motor controller (PID) =
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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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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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=== Approach "Hall sensor module" ===
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<gallery>
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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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  File:Speedcontrol.png | Motor speed settings
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  File: Odometry_motor_pid_controller.png
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* ACS712ELC-05A (185mV/A, max. 5A)
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</gallery>
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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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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“