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Software

Control System

To get to know all the possibilites and functions which the control system provides please have a look into the Control System described on the eeros wiki.

Control System of the Delta roboter

Lets start with the blue boxes at the centered bottom of the diagramm. This boxes represent the motor package, included the motor, the encoder and the gear. The encoders of the motor packages are defined as “Peripheral Input”. This “Peripheral Inputs” are described in the HAL configuration file. To initialze the encoder inputs, you'll have to call the constructor of the “Peripheral Input” and add the respective “signalId” from the HAL file as parameter, e.g.

eeros::control::PeripheralInput<double> encoder1("enc1");

Because the HAL is configured correctly, we get the current position in radian of each encoder. Next up, the “Mux” collects the four encoder values and puts them into a “AxisVector”. “AxisVector” is defined as

using AxisVector = eeros::math::Matrix<4, 1>;

The “Direct Kinematic” converts the current radian positions of the encoders into cartesian coordinates. The output AxisVector now contains the x, y, z and phi value of the TCP.
Now we switch to the left. We got two possible input types. The “Mouse Input” gets the movement of the mouse and all the buttons attached to it, we use this block to manually control the Delta robot. The output of the “Mouse Input” is an AxisVector containing x, y, z and phi values. X and y change with the mouse movement. Z changes when scrolling up or down on the mouse wheel. Phi changes when pressing the mouse wheel to left or to right. To initialize the “Mouse Input” you have to add the input device as parameter to the constructor, e.g.

eeros::control::MouseInput mouse("/dev/input/event1");

Do not use “/dev/input/mice” or “/dev/input/mouse0” as parameter. The “Mouse” of EEROS uses mouse events.
The “PathPlanner”, as the name says, plans the path to the next point. This is used for auto moving of the Delta robot.

The “Motor Model” gets the actual speed and the calculated torque as input, and outputs the desired voltage for each motor.
The “voltageSetPoint” serves for the initializing of the encoder. This block is no longer used after reaching Safety Level “systemReady”.

Safety System

To get more informations and details how the Safety System works, please have a look into the Safety System described on the eeros wiki. Safety System of the Delta roboter

The forward paths of the Safety System are on the righthand side of the diagramm. The backward paths on the lefthand side.
The entry level of the Safety System is “slOff”. In the file “delta.cpp” the Safety Event “doSwInit” gets triggered. In case of any failure in the Control System, the Safety Event “doEmergency” gets registered in the timedomain.

Sequencer & Sequences

For more informations how Sequences and the Sequencer work, have a look into Sequencer on the eeros wiki. Sequences of the Delta roboter When the homing of the Delta robot is completed the “Main Sequence” gets started. In this sequence, other sequences get added, dependent on the current Safety Level. The first activated Safety Level is “slAutoMoving”. So the “Main Sequence” starts the “Sort Sequence” and waits until its finished, after that, the “Shuffle Sequence” gets started, and once again, the “Main Sequence” waits until this is finished. After that, the “Main Sequence” gets restarted, and if no Safety Event got triggered, the “Sort Sequence” and the “Shuffle Sequence” gets started again.
The “Sort Sequence” and the “Shuffle Sequence” are equipped with a Monitor. This Monitor checks the “Move Mouse Condition”. If the mouse gets moved, or a button on the mouse gets pressed, the Condition returns “true”, the current running sequence gets aborted and the “Move Mouse Exception Sequece” gets started. This sequence moves the TCP back to init position, and triggers the Safety Event “doMouseTeaching”. The “Main Sequence” now starts the “Mouse Sequence”. As long as the mouse gets moved, or buttons are pressed, the “Mouse Sequence” will be active. This sequence is equipped with a “Time Out Monitor”. If the mouse doesn't send any event for 2 seconds, this Monitor triggers the “MouseSequenceTimeOutExpectionSequence”. This “Exception Sequence” aborts the “Mouse Sequence”, moves the TCP back to the init position and triggers the Safety Event “doAutoMoving”.

The “Calibration Sequence” can be started by triggering the Safety Event “doCalibrating”. This can be done by pressing the red button until this lights up. Press and hold the red button for 2 seconds, this will trigger the Safety Event “doCalibrating”. When finished with calibrating, press the red button once again. Press the green button to get back in normal operation mode.

HAL

To get more information about the Hardware Abstraction Layer and how it works, please have a look into the HAL described on the eeros wiki.
EEROS for the Beagle Bone Blue is using the robotis_cape_library. You'll find the wrapper and its functions in the bbblue-eeros folder.

Configure the motors

If you want to run a motor with EEROS you need to define a Peripheral Output with the respective “signalId” used in the HAL-Configuration file. As you can see in the HAL-Configuration file for the Delta roboter in “subdevice2” the type for the motors is set to “AnalogOut”. In this subdevice section the 4 motors are configured to match the functions of the robotics_cape_library. In the EEROS application for the Delta roboter you can set a motor voltage of -8.0V to 8.0V. The HAL gets this values and wraps it to match the values of the robotics_cape_library which then runs the motors with the desired voltage. HAL-Configuration for the motors

Configure the encoders

The Delta roboter has two different motors with different encoders and gears. You'll find the datasheets of the two types here.

Calculate the Axis Motor

The Axis Motor is equipped with gear with gear ratio of 76:1 and with the encoder ieh2-4096, which provides 4096 lines per revolution ( =16384 counts per revolution). So for one full turn on the gear axis, the encoder sends 16384*76 = 1245184 counts. This is the input value for the HAL.
In the EEROS application we don't want to calculate everytime the respective radian value from this counts, so we do this in the HAL. To do that, we need to add some “blocks”.
Start with the gear:
one full turn on the gear axis (=2*PI) equals to 76 turns of the motor axis. Next up, for one revolution of the motor axis, the encoder sends 4096 lines. So if we turn the gear axis for one revolution, the motor axis turns 76 times and the encoder sends 76*4096 = 311296 lines. The last block is the FQD. It converts the lines of the encoder into single counts. One line equals to 4 counts.
HAL config for ieh2 encoder The Axis Motors have mechanical upper and lower limits.

Upper limitLower limit
Lower limit of the Axis Motor
Upper limit calculation below.Measured on the Delta robot, γ is about 5°.

The upper limit calculates with the following two equations:

(1) tan(β)=(15-y)/17.5
(2) cos(β)=6/y

Transform this two equations until you get

(3) 17.5*sin(β)-15*cos(β)=-6

The subraction of a cosine function from a sine function results in another sine function with phase shift. So we are looking for a function in form of

(4) A*sin(β+φ) = 17.5*sin(β)-15*cos(β)

By using the addition theorem we get

A*sin(β+φ) = A*sin(β)*cos(φ)+A*cos(β)*sin(φ)

Now we can compare the coefficients from sin(β) and cos(β)

(5) 17.5=A*cos(φ)
(6) -15=A*sin(φ)

By dividing (6) by (5) we get

-15/17.5=sin(φ)/cos(φ)=tan(φ) → φ = arctan(-15/17.5)=-40.60°

Take the square of each function and add them together results in

17.52+(-15)2 = A2*(sin2(φ)+cos2(φ)) = A2
A = sqrt(17.52+(-15)2) = 23.048

Inserting the values in (4)

23.048*sin(β-40.60°)=17.5*sin(β)-15*cos(β)=-6

we can now solve for β

β=arcsin(-6/23.048)+40.60° = 25.51°

The maximum angle which the Gear axis can turn is 90°+5°+25°=120°.

Calculate the TCP Motor

HAL config for HEM3 encoder As described in the previous encoder, the values are now:

  • gear ratio: 120:1
  • lines per revolution: 256

So one turn on the gear axis results in 256*4*120 = 122880 counts.

TCP limit The TCP rotation is also limited. The maximum turn angle is calculated as follows:

sin(γ/2) = r/R
γ=2*arcsin(r/R)=3.438°

Thats the value for one side. The other side is identical, so the maximum angle to turn is

360°-2*3.438°=353°.

software.txt · Last modified: 2018/12/14 08:59 by fink