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Zeile 1: Zeile 1:
 
= Abstract =
 
= Abstract =
−
Ardumower's design 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]]):
+
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]]):
−
* Two motors (with integrated gearing) for driving (wheel motors), and encoder (for distance, direction and speed control)
+
* 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)
 
* One motor (with high rotation speed) for mowing (mower motor)
  
−
To control a motor, it requires a 'motor driver'. Ardumower uses a dual MC33926 motor driver, so two channels for left and right 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.
 +
 
 +
[[File:Ardumower_motordriver_overview.png|800px]]
  
 
= Voltages =
 
= Voltages =
−
Although there exist 12V motors and 24V motors, as in all modern systems, the Ardumower uses 24V motors.
+
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
  
−
= Wheel motors =
 
 
<gallery>
 
<gallery>
 +
File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
 +
File: Pcb_mc33926.jpg | PCB and MC33926
 +
File:Mc33926.jpg | MC33926 pinout
 +
File:MC33926_schematics.jpg | MC33926 schematics
 +
</gallery>
 +
 +
* [https://www.youtube.com/watch?feature=player_embedded&v=DokrJiVzX2I Video instructions: Dual MC33926]
 +
 +
For wiring of motor drivers, protector and motors, please open manual in section Protector PCB.
 +
 +
=Protector PCB=
 +
[[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>
 +
File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
 +
File:Protector_pcb2.jpg | Protector PCB
 +
File:Protector_wiring.png | Protector PCB wiring
 +
File:driver_hw_protection.png | Protector PCB schematics
 +
</gallery>
 +
 +
* [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!)]
 +
 +
= Wheel motors wiring =
 +
<gallery>
 +
  File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
 
   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)
 
   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)
 +
  File: magnetic_encoder.PNG | Motor wiring
 
   File: wheel_motor_diagram.png | Ardumower gear motor curve (motor only)
 
   File: wheel_motor_diagram.png | Ardumower gear motor curve (motor only)
−
   File:decrease_motor_noise.png | Decrease motor noise
+
   File: Ardumower_gearbox.png | Gearbox specification
−
  File: magnetic_encoder.PNG | Motor encoder wiring
+
 
</gallery>
 
</gallery>
 
The two left and right gear motors are controlled independently (aka 'differential driving') to:
 
The two left and right gear motors are controlled independently (aka 'differential driving') to:
Zeile 21: Zeile 52:
 
* steer the robot left/right
 
* steer the robot left/right
  
−
The Ardumower wheel motor features:
+
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 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 nomeinal speed) up to 14 degree) [http://www.robotshop.com/blog/en/drive-motor-sizing-tool-9698 see calculator]
+
* 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]
−
* Integrated encoders, so it can measure the rotation speed, the distance and the direction (see [[Odometry]] for more information) - Encoders are REQUIRED for Ardumower software.
+
* Integrated encoders, so it can measure the rotation speed and the distance
 
* 24V  (load current ~1A)
 
* 24V  (load current ~1A)
  
−
=Protector PCB=
+
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)
  
−
[https://github.com/Ardumower/ardumower/raw/master/pcb/megashield_svn_1.2_geschlossen/Dokumentation/WORKSHOP%20Protector-Board.pdf Protector board] is adviced to be used between controller and motor.
+
For right motor, use Protector board Motor_2_OUT(1,2) accordingly.
  
−
=== Motor driver ===
+
= Wheel motors odometry wiring =
  
−
Features: up to 3A with integrated current sensor and thermal shut-down protection, for all kind of robot mowers)
+
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>
−
File:Mc33926.jpg | pinout
+
  File: magnetic_encoder.PNG | Motor wiring
−
File:Mc33926_example.jpg | jumpers
+
  File: ardumower_odometry_encoder.jpg | Encoder signal
−
File:MC33926_schematics.jpg | schematics
+
−
File:Mc33926_current_limiter.jpg | automatic current limiter
+
−
File:Motor_pwm_50_percent_transients.jpg | Motor start 50% PWM transients
+
−
File:driver_hw_protection.png | Peak/EMF protection
+
 
</gallery>
 
</gallery>
  
−
'''
+
Motor odometry wiring (left motor):
−
  M1_FB    --- pinMotorLeftSense A1
+
  Motor (brown) ---- PCB VCC
−
  M1_SF    --- pinMotorLeftFault 25
+
  Motor (green) ---- PCB GND
−
M1_PWM_D1 --- connect with jumper to GND
+
  Motor (blue)  ---- PCB OdometryLeft (3)
−
  M1_PWM_D2 --- connect with jumper to VDD
+
  Motor (purple) ---- PCB OdometryLeft (4)
−
  M1_IN1    --- pinMotorLeftPWM 5 
+
−
M1_IN2    --- pinMotorLeftDir 31
+
−
EN        --- pinMotorEnable  37
+
−
M2_FB    --- pinMotorRightSense A0
+
−
M2_SF    --- pinMotorRightFault 27
+
−
M2_PWM_D1 --- connect with jumper to GND
+
−
  M2_PWM_D2 --- connect with jumper to VDD
+
−
M2_IN1    --- pinMotorRightPWM  3  
+
−
  M2_IN2    --- pinMotorRightDir 33
+
−
EN        --- pinMotorEnable  37
+
−
VDD      --- Arduino 5V
+
  
−
= Mower motor and driver =
+
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 =
 
<gallery>
 
<gallery>
 +
File: Ardumower_motordriver_overview.png | PCB, MC33926, protector and motors
 
File: ardumower_mower_motor.jpg | Ardumower mower motor
 
File: ardumower_mower_motor.jpg | Ardumower mower motor
 
File: Mower_motor_curve.png | Ardumower mower motor curve
 
File: Mower_motor_curve.png | Ardumower mower motor curve
Zeile 73: Zeile 101:
 
* Quiet mowing (you cannot hear it)
 
* Quiet mowing (you cannot hear it)
 
* 24V, load current ~1.0A  (L=2.8mH, R=1.9ohm)
 
* 24V, load current ~1.0A  (L=2.8mH, R=1.9ohm)
−
 
−
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.
 
  
 
[[File:warning.png]]'''Security note: For security reasons, always remove mower blades in your first tests!'''
 
[[File:warning.png]]'''Security note: For security reasons, always remove mower blades in your first tests!'''
  
−
<gallery>
 
−
File: Ardumower_mower_motor_circuit.png | NOTE: only for demonstration! See real [http://wiki.ardumower.de/index.php?title=Ardumower_PCB schematics] for concrete wiring
 
−
</gallery>
 
  
−
= Choosing a driver =
+
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)
  
−
When purchasing a motor driver, consider...
+
= Motor decrease noise =
−
* max. thermal load (short-circuit current)
+
−
* price
+
  
−
= Starting current =
+
Here's how you can decrease motor noise:
−
Here are some measurements of the Ardumower motor's starting current (peak):
+
−
 
+
−
Starting current:
+
−
* Gear motor: 15A (starting current peak)
+
−
* Mowing motor: 20A (starting current peak)
+
  
 
<gallery>
 
<gallery>
−
File: Messung_einschalt_spitzen.jpg | Gear motor start current (peak)
+
  File:decrease_motor_noise.png | Decrease motor noise
 
</gallery>
 
</gallery>
  
−
= Short-circuit current =
+
* [https://github.com/Ardumower/ardumower/blob/master/Dokumentation/Motor%20Entstoerung/Motor%20EntstoerungREV20150531.pdf Instructions: Motor-decrease noise REV20150531]
−
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:
+
* [http://www.ardumower.de/media/kunena/attachments/1725/Motor-EntstoerungREV20150531.pdf (English comments)]
  
−
Battery === Ampere meter === Motor
 
  
−
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).
+
= Motor controller (PID) =
−
 
+
−
'''Warning'''
+
−
 
+
−
* always remove blades
+
−
* only connect battery for a short period (1-5 seconds)
+
−
* always use cables with sufficient wire cross section
+
−
 
+
−
Example measurement:
+
−
 
+
−
* Rotenbach SPM08-320
+
−
** Wheel motor: 8A
+
−
** Mowing motor:
+
−
 
+
−
* Ambrogio L50
+
−
** Wheel motor: 4,5A
+
−
** Mowing motor: 22A
+
−
 
+
−
* Tianchen TC-G158
+
−
** Wheel motor: 5,4A
+
−
** Mowing motor: 16A (both 32A)
+
−
 
+
−
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).
+
−
 
+
−
 
+
−
= Current sensor =
+
−
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.
+
−
 
+
−
== Approach "Hall sensor module" ==
+
−
This is the recommended approach for sensing current. These current sensor modules are available for different current ranges.
+
−
 
+
−
* ACS712ELC-05A (185mV/A, max. 5A)
+
−
* ACS712ELC-20A (100mV/A, max. 20A)
+
−
* ACS712ELC-30A (66mV/A, max. 30A)
+
−
* The lower the range, the more precise the measurement.
+
−
 
+
−
== Approach "Shunt resistor (circuit)" ==
+
−
The current flows across a very small resistor (0.5 Ohm) and the voltage drop is measured
+
−
 
+
−
 
+
−
<gallery>
+
−
File: L298n_module_circuit.jpg
+
−
</gallery>
+
−
 
+
−
=Further links=
+
−
#[http://www.ardumower.de/index.php/en/forum/maehwerk/74-10a-pwm-controller-modul-fuer-den-arduino 10A PWM controller module modification]
+
−
 
+
−
== 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):
 
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):
  
Zeile 158: Zeile 128:
 
   File: Odometry_motor_pid_controller.png
 
   File: Odometry_motor_pid_controller.png
 
</gallery>
 
</gallery>
−
 
−
 
−
= Programming =
 
−
 
−
== Motor variables ==
 
−
 
−
    // --------- wheel motor state ----------------------------
 
−
    // wheel motor speed ( <0 backward, >0 forward); range -motorSpeedMaxRpm..motorSpeedMaxRpm
 
−
    //                                  [Default value]
 
−
    float motorAccel  ;          // motor wheel acceleration - only functional when odometry is not in use
 
−
                                // (warning: do not set too high) [1000]
 
−
    int motorSpeedMaxRpm  ;    // motor wheel max RPM  [25]
 
−
    int motorSpeedMaxPwm  ;      // motor wheel max Pwm  (8-bit PWM=255, 10-bit PWM=1023) [255]
 
−
    float motorPowerMax  ;      // motor wheel max power (Watt)
 
−
    PID motorLeftPID;            // motor left wheel PID controller [Kp=1.5 , Kd=0.29, Ki=0.25]
 
−
    PID motorRightPID;          // motor right wheel PID controller
 
−
    float motorSenseRightScale ; // motor right sense scale (mA=(ADC-zero)/scale)
 
−
    float motorSenseLeftScale ;  // motor left sense scale  (mA=(ADC-zero)/scale)
 
−
    int motorRollTimeMax ;      // max. roll time (ms)
 
−
    int motorRollTimeMin  ;      // min. roll time (ms)
 
−
    int motorReverseTime ;      // max. reverse time (ms)
 
−
    long motorForwTimeMax;      // max. forward time (ms) / timeout
 
−
    float motorBiDirSpeedRatio1 ;// bidir mow pattern speed ratio 1
 
−
    float motorBiDirSpeedRatio2 ;// bidir mow pattern speed ratio 2
 
−
    bool motorRightSwapDir    ; // inverse right motor direction?
 
−
    bool motorLeftSwapDir      ; // inverse left motor direction? 
 
−
    int motorLeftSpeedRpmSet ;  // set speed
 
−
    int motorRightSpeedRpmSet ;
 
−
    float motorLeftPWMCurr ;    // current speed
 
−
    float motorRightPWMCurr ;
 
−
    int motorRightSenseADC ;
 
−
    int motorLeftSenseADC ;
 
−
    float motorLeftSenseCurrent ;   
 
−
    float motorRightSenseCurrent ;
 
−
    float motorLeftSense ;      // motor power (range 0..MAX_MOTOR_POWER)
 
−
    float motorRightSense ;
 
−
    int motorPowerIgnoreTime;
 
−
    int motorZeroSettleTime;    // how long (ms) to wait for motor to settle at zero speed
 
−
    int motorLeftSenseCounter ;  // motor current counter
 
−
    int motorRightSenseCounter ;
 
−
    unsigned long nextTimeMotorSense ;
 
−
    unsigned long lastSetMotorSpeedTime;
 
−
    unsigned long motorLeftZeroTimeout;
 
−
    unsigned long motorRightZeroTimeout;
 
−
    boolean rotateLeft;
 
−
    unsigned long nextTimeRotationChange;
 
−
 
−
== Motor Methods ==
 
−
 
−
First the basic function that control the pwm to each motors:
 
−
  void setMotorPWM(int pwmLeft, int pwmRight, boolean useAccel);
 
−
 
−
A general methods to test motors
 
−
  void testMotors();
 
−
 
−
Then, there are several MotorControl methods according to mower state :
 
−
 
−
if current state is 'STATE_PERI_TRACK' then
 
−
  void motorControlPerimeter();
 
−
 
−
 
−
  void motorControlImuRoll();
 
−
 
−
  void motorControlImuDir();
 
−
 
−
for all other case : 
 
−
 
−
  void motorControl();
 
−
  // This method calculate pwm to set in order to respect rpm setpoint according current rpm and Kp, Ki, Kd parameter
 

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“