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Autopilot Kanardia, Installation Manual

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Autopilot Installation Manual

5.2

Step Change and Response

Typical block representation of the controller with feedback is shown on fig-
ure 13. The input to

PID

controller is the difference between reference and

measured process value. Output of the controller must control the process to
reduce the difference. Controller performance depends heavily on the accu-
racy of the sensed process variable and the precision of the actuator.

PID

controller

Aircraft

(Process)

+   

Reference

-

Process variable

Figure 13:

Typical PID controller block diagram.

If you are interested in PID controller, a good start may be the Wikipedia
article,

https://en.wikipedia.org/wiki/PID_controller

.

5.2

Step Change and Response

Controller tuning is an iterative process. The operator triggers a step change
of the reference value for each loop observing the aircraft response. Based on
the aircraft response the terms of the controller are modified to get optimal
ones. Analysis of response needs few technical terms which are explained with
a figure 14:

Time

V

a

ria

bl

e

1

2

3

4

5

Figure 14:

Step response of closed loop system.

1. Reference step change.

27

©

Kanardia

2016-2020

Summary of Contents for Kanardia

Page 1: ...Autopilot Installation Manual Kanardia d o o November 2020 Revision 2 1 ...

Page 2: ......

Page 3: ...sa 3 0 In short the license gives you right to copy reproduce and modify this document if you cite Kanardia d o o as the author of the original work you distribute the resulting work only under the same or similar license to this one Credits This document was written using TeX Live L A TEX based document creation system using Kile running on Linux operating system Most of the figures were drawn us...

Page 4: ...iption 1 0 Aug 2015 Initial release 1 1 Maj 2016 Tuning notes were added 1 2 Jul 2016 Tuning table expanded 2 0 Feb 2020 Complete Manual rework 2 1 Nov 2020 Updated for changes in software version 3 8 Amigo and Nesis Aetos windows 4 Kanardia 2016 2020 ...

Page 5: ...stallation 11 2 1 Servo Motor 12 2 2 Servo Arm 13 2 3 Servo Arm Limiter 13 2 4 Servo Arm Safety Pin 14 3 Electrical Installation 14 3 1 Electrical Power 14 3 2 CAN Bus 15 3 3 External Push Button 15 3 3 1 Autopilot Quick Disconnect 16 3 3 2 Autopilot Level 16 3 4 Joyu Command Stick 16 4 Configuration 16 4 1 Overview 17 4 2 Autopilot Settings 17 4 2 1 Servo Configuration 18 4 2 2 Ground Test 20 4 2...

Page 6: ...ning Rules 30 6 In Flight Tuning 31 6 1 Elevator 31 6 1 1 Pitch tuning 32 6 1 2 Vertical speed tune 36 6 2 Aileron tune 39 6 2 1 Roll tune 39 6 2 2 Heading tune 40 6 3 Fine tuning 41 6 3 1 Roll feed forward 41 6 3 2 Motor power 42 7 Quick Configuration 42 7 1 Configure Servos 43 7 2 Direction Test 43 7 3 Operating Limits 43 7 4 Tuning 44 8 Safety Measures 44 8 1 Automatic Disable 45 8 2 Manual Dis...

Page 7: ...ing Form 47 B Parameters For Known Airplanes 48 B 1 Ekolot Topaz 48 B 2 Pipistrel Sinus 48 B 3 Aeropilot Legend 540 49 B 4 Evector Eurostar EV97 49 B 5 Aerospool Dynamic WT9 50 B 6 Roko Aviation 50 B 7 Aeroprakt 51 B 8 Direct Fly 51 B 9 Comco Ikarus 52 7 Kanardia 2016 2020 ...

Page 8: ...ith special attention This icon denotes background information about the subject This icon denotes a tip In the text Shall Should appear frequently Shall the use of this term indicates a requirement Should the use of this term indicates a characteristics that is not required but it is highly recommended 1 2 Intended Use The autopilot is designed to help a pilot in stable controllable flight condit...

Page 9: ...te itself automatically Autopilot does not use any information from Magu magnetic compass 1 4 Minimal Configuration Most modern light airplanes can be controlled during a stable flight by con trolling elevator and aileron only An autopilot function can be achieved using the following minimum configuration Two servo motors that are mechanically connected with the airplane command system One motor c...

Page 10: ...egrated AD AHRS GPS device which provides all sensor data The display has several buttons and a knob that allow pilot control over the system In addition touch screen can be also used on Nesis III Simple RJ45 cables a k a Ethernet cables are needed to connect them together The devices are communicating using the CAN bus system which is integral part of almost all Kanardia devices In this combinati...

Page 11: ...uested altitude sets wanted vertical speed and the vertical speed loop sets wanted pitch The pitch loop then controls the elevator by minimizing the difference between requested and actual pitch Aileron works in a similar way Requested direction sets the required roll angle and the roll loop controls the aileron trying to minimize the difference between requested and actual roll angle This means t...

Page 12: ...is mandatory to resolve these questions prior to flight of the aircraft CAUTION Improper installation could result in lost aircraft controls injury or death 2 1 Servo Motor The servo motor must be installed in a fixed position It must be attached with all four mounting screws The motor mount should be provided by aircraft manufacturer and has to be adapted to specific airplane model The motor shou...

Page 13: ... at least very close to this ideal case When command is in its extreme position the angle between the command rod and the arm must never be more than 150 or less then 30 Under no circumstances the servo arm is allowed to come into position called over center the position at which the primary aircraft control would lock up and can result in fatal crash A mechanical stops must be applied to prevent ...

Page 14: ...t specific torque applied on servo arm The airplane command system must be capable to withstand the forces in the command system required to break the safety pin 3 Electrical Installation Servo motor has two electrical connections The first one provides power for the electrical motor and the second one connects controlling device with the CAN bus The controlling device is hidden inside the servo m...

Page 15: ... The CAN bus goes trough Nesis or Aetos where it is internally connected to AD AHRS GPS module On the servo side T junction is needed and a short connection is made from T to the servo controller Airu AD AHRS GPS T T CAN bus to other devices to other devices Nesis III or Aetos Ctrl Ctrl Figure 4 Typical CAN bus connection for Nesis Aetos based minimal autopi lot configuration Please note that CAN ...

Page 16: ...this function must be configured In the case of Amigo it is activated by a long press on the external button No configuration is necessary 3 4 Joyu Command Stick Alternatively Joyu command stick can be also used Joyu has multiple pro grammable buttons and one or more of its buttons can be assigned to operate the autopilot Short press on the button should be used for autopilot disconnect and long p...

Page 17: ...ne an envelope of values which must be met for AP to operate This is a very important safety feature 4 Autopilot controller parameters are set Most of them can be set on the ground but some must be adjusted during flight tests 5 Autopilot is tuned which is the most difficult part This can be per formed only in flight Several controller values must be determined First three steps shall be set on th...

Page 18: ...ving the con trols See section 4 2 2 Limits is used to define valid operation envelope of the autopilot section 4 2 3 Parameters is used to define various controller parameters section 4 2 4 Tuning is an in flight operation used to setup PID terms of the controller loops for the elevator and aileron See section 5 5 4 2 1 Servo Configuration When setting up an autopilot configuring the servos is th...

Page 19: ... mechanical connection If servo with given serial number is connected to the aileron then the function must also be Aileron Change the function if necessary You can choose between Aileron or Elevator Reversed has values No or Yes Choosing correct value is a guessing game Start with No and if ground test described in section 4 2 2 fails change it to Yes and vice versa Power defines how much power t...

Page 20: ...cumstances this shall be zero but this is seldom the case Max speed is the maximal speed of servo arm movement in degrees per sec ond This value is usually set between 10 and 30 deg s PPR tells how many pulses are needed for one rotation of internal stepper motor always 200 for current servos This is servo motor characteris tics and shall not be changed Reduction is the gearbox reduction factor be...

Page 21: ...y in the neutral position and execute the Forward Backward commands You will feel servo movement in your hand If a movement appears in wrong direction go back to the Servo Config and toggle the Reversed option If servo moves a wrong command go back to the Servo Config and modifiy the Function Check both servos Do not start tuning until you are 100 sure that ground test works correctly 4 2 3 Operat...

Page 22: ... 35 or less Max pitch maximal allowed pitch for autopilot operation Set this to 12 or less All limits must be checked with a flight test after the tuning has been com pleted The limits must be set conservatively Make any adjustments with great care Flying with the autopilot at a slow speeds is not allowed It would be ex tremely dangerous The dynamic characteristics of the airplane at low speed can...

Page 23: ...g the zero angle If this virtual relative angle exceeds the Max arm mv value the system reports a Motor slip error Namely servo does not measure angle directly but it is counting steps from zero position If motor is slipping servo torque is too small these counts will accumulate to a number virtual angle large enough to trigger the error Due to slips the arm did not move that much in reality Pitch...

Page 24: ...nge in roll the controller will limit the speed of change to the value entered here The airplane will therefore make a smooth transition Max VS rate is the rate of change of the target vertical speed it has dimen sion of acceleration Similar as above but now for vertical speed Turn comp defines amount of elevator compensation that is required when airplane is executing a turn Pitch will be slightl...

Page 25: ...esents the loop target value The target value is changed and airplane response is observed in the chart The target is drawn in magenta color and the response is in yellow P I and D terms are controller terms The controller tries to reduce an error between a target magenta value and an actual value yellow Error is a difference between target and actual value P term defines controller s proportional...

Page 26: ...k of controlling parameter A PID controller continuously calculates an error value as the difference between a de sired reference and a measured process variable roll pitch VS and heading It applies a correction based on proportional integral and derivative terms denoted P I and D respectively During tuning the operator is searching for optimal terms inside each loop roll pitch vertical speed and ...

Page 27: ...eference Process variable Figure 13 Typical PID controller block diagram If you are interested in PID controller a good start may be the Wikipedia article https en wikipedia org wiki PID_controller 5 2 Step Change and Response Controller tuning is an iterative process The operator triggers a step change of the reference value for each loop observing the aircraft response Based on the aircraft resp...

Page 28: ...own on figure 15 Note that there are two feedback loops and two controllers Inner controller is controlling pitch of the aircraft and outer is controlling its vertical speed PID Reference Vertical Speed PID Elevator Aircraft Pitch Vertical Speed Figure 15 Elevator cascade PID controller block diagram The important fact of this system is that outer loop response depends on the performance of the in...

Page 29: ...ill slip Slipping motor is unable to control the aircraft Resolve slip issues on either axis before proceeding either by increasing motor torque changing hole on control arm or switching to a larger servo If the motor is slipping there are no software options You can notice the slipping as a sudden small jump of the stick The most common behavior of the aircraft with one of the servos slipping is ...

Page 30: ...y points the pilot s attention will be divided between documentation tuning autopilot and maintaining situational awareness An extra pair of eyes looking out is very helpful 5 6 Tuning Rules The operator should follow following rules during in flight tuning and testing the autopilot Make notes during flight Change only one parameter or term at once Make small changes of parameters ot terms Test ev...

Page 31: ...yes Figure 16 Elevator tune Elevator control consist of two cascaded control loops pitch and vertical speed The operator shall tune the pitch loop first Without properly operating pitch loop the VS loop is impossible to tune During in flight tuning the elevator will be controlled by the autopilot servo The pilot shall maintain aircraft leveled with ailerons during the elevator tuning but it shall ...

Page 32: ...ery step change set reference to 0 and wait for the aircraft to stabilize Follow provided flow charts for tuning each controller term P term shall be tuned following flow chart shown in figure 6 1 1 Start with low P term and then gradually increasing it until you reach satisfactory response 1 Set 0 degrees reference angle 2 Steady state Wait enough time for con troller to stabilize Around 10 secon...

Page 33: ...e reference angle by 3 5 degrees This depends on aircraft In our example we choose 4 degrees 4 Observe the response Wait approx 10 15 seconds 5 Modify the I term according on the air craft response Please see example tun ing on figure 17 for example responses and appropriate actions If you would like to decrease the response time I term should be decreased 6 Repeat Go back to step 1 Wait 10 second...

Page 34: ...ons If you would like to increase damping you should increase the value of D term 6 Repeat Go back to step 1 Wait 10 seconds Set Reference to 0 D 0 0 s Wait 10 seconds Is response OK Step change Reference 3 5 DONE D D 0 2 s no yes Testing After successful tuning of pitch loop the operator shall test the pitch loop with different reference angles The aircraft response shall be with small overshoot ...

Page 35: ...w b P still too low c P ok Small overshoot d Start I for pitch is 8s e Lower I better f Lower I even better g Add D I 20 h D term too big D D 2 i Decrease I slightly DONE j Test also in minus Figure 17 Example of pitch tuning process 35 Kanardia 2016 2020 ...

Page 36: ... speed Do not worry if the aircraft pitches down after initial pitch up reaction This is normal and it is related to the loss of airspeed The tuning of I term should handle this situation If the aircraft starts to oscillate with large amplitude around pitch axis the P term is too high You will have to decrease it to the half of the current value Problems In case that it is impossible to tune the a...

Page 37: ...all value The starting D term should be around I term 20 Increase it only if you do not observe any oscillations The maximum D term should not exceed I term 5 Testing After tuning the operator should test the PID terms with different vertical speeds both in climb and in descend Please note the autopilot will not automatically adjust the airspeed If the airspeed is too high or too low the autopilot...

Page 38: ...oo low b P still too low c P still too low d P is now just enough e Start value for I f Lower I even better g I should be ok h D I 20 i Increase D slightly DONE j Test also in minus Figure 18 Example of vertical speed tuning process 38 Kanardia 2016 2020 ...

Page 39: ...meter is set to 1 0 this means that autopilot will try to correct the error of 5 with an roll rate of 5 s For start it should be set to 1 0 This value is fine for most installations P term With Roll rate gain parameter set to 1 0 we are now tuning the roll rate and not the roll angle For this you will notice dashed lines in tuning dialog which marks the selected Maximum Roll Rate parameter Before ...

Page 40: ...direction Figure 19 Example of roll rate tuning process 6 2 2 Heading tune If the roll control loop is operating properly the tuning of the heading loop is usually simple However the operator must check that response of the aircraft is good enough under operating all conditions The starting values for P term shall be 1 0 and I term 25 0s The step angle for testing the 40 Kanardia 2016 2020 ...

Page 41: ...hanges of reference heading Try to test with small step change of 5 If there is too much overshoot increase the I term D term shall remain set 0 0 6 3 Fine tuning There are some parameters that should be adjusted after the basic tuning is done This parameters will improve autopilot performance 6 3 1 Roll feed forward This parameter sets how much the elevator control is pulled or pushed during the ...

Page 42: ...k is very hard to overcome the torque of the motor the torque of the appropriate axis should be lowered This will reduce the current consumption of the motor and it will reduce the motor heating Also the pilot will be able to override the autopilot with more appropriate force 7 Quick Configuration This is a quick reminder of Nesis Aetos commands inputs required to config ure the autopilot system f...

Page 43: ...t Options Service Mode Autopilot Test Press move forward backward left right The yoke stick should move in the correct direction If the movement is opposite change the Reversed parameter in Servo Configuration 7 3 Operating Limits Options Service Mode Autopilot Limits Minimum IAS 140 km h Maximum IAS 200 km h Maximum vario 6 m s Maximum Roll 30 Maximum Pitch 12 Values shown above are given for exa...

Page 44: ... autopilot is directly linked with aircraft commands thus it presents high risk if something fails or goes wrong Kanardia autopilot is using following safety measures in order to reduce this risk to a minimum Automatic disable when aircraft is outside safe operating limits Multiple Manual disable options Servo power switch immediately cuts the power of servo motors Motor override the servo motor c...

Page 45: ...able option from the autopilot menu of Nesis Aetos 2 On Nesis Aetos press the User button when the autopilot menu is active double click on user button 3 On Nesis Aetos make a long press on the User button the long press function must be properly configured 4 When an external push button is installed on a command stick press the button to disable the autopilot Nesis Aetos or Amigo must be properly...

Page 46: ...nical Disable The servo motor torque is small enough that it can be overridden by higher force in the command stick even when servo is operating with 100 torque However the commands feel jerky and precise steering is a bit challenging Safety pin is the inserted between the servo arm and the servo motor shaft In the very unlikely case of blocked motor or blocked gears pilot can use force on the com...

Page 47: ...vator Aileron Setting Elevator Aileron Model Reversed Lever Power Lever hole Hold pwr PPR Backlash Reduction Top speed Operating limits Max IAS Max roll Min IAS Max pitch Max VS Configuration parameters Max arm mv Max pitch rate Pitch target Max roll rate Roll target Max VS rate VS target Turn comp Roll rate gain Tuning parameters Parameter Pitch Vario Roll Heading P term I term D term 47 Kanardia...

Page 48: ... a different hole in the servo arm etc then these values may not be completely suitable and re tuning is necessary Some loops given below are using special values RFF means Roll Feed For ward VS is Vertical Speed RRG means Roll Rate Gain B 1 Ekolot Topaz Table 1 Topaz configuration parameters Max arm mv 40 Max pitch rate 10 s Pitch target 12 Max roll rate 3 s Roll target 20 Max VS rate 1 5m s 2 VS...

Page 49: ...S Roll Heading P term 0 5 0 02 0 5 1 0 I term 7 0 12 0 8 0 25 D term 0 16 0 2 0 02 0 2 B 3 Aeropilot Legend 540 Table 5 Legend 540 configuration parameters Max arm mv 40 Max pitch rate 5 s Pitch target 10 Max roll rate 3 s Roll target 20 Max VS rate 1 0m s 2 VS target 3m s Turn comp 0 2 Roll rate gain disabled Table 6 Legend 540 PID values Parameter Pitch VS Roll Heading P term 0 65 0 017 0 9 0 6 ...

Page 50: ...meter Pitch VS Roll Heading P term 0 4 0 025 0 7 0 9 I term 7 0 12 0 8 26 D term 0 0 0 2 0 2 0 2 B 5 Aerospool Dynamic WT9 Table 9 WT9 configuration parameters Max arm mv 30 Max pitch rate 3 s Pitch target 10 Max roll rate 3 s Roll target 20 Max VS rate 1 0m s 2 VS target 2 5m s Turn comp 0 2 Roll rate gain 2 0 Table 10 WT9 PID values Parameter Pitch VS Roll Heading P term 1 2 0 024 0 6 1 5 I term...

Page 51: ... Pitch VS Roll Heading P term 1 2 0 017 0 6 0 6 I term 6 5 15 0 4 5 26 D term 0 52 0 32 0 4 0 2 B 7 Aeroprakt Table 13 A22 A32 configuration parameters Max arm mv 30 Max pitch rate 4 s Pitch target 10 Max roll rate 5 s Roll target 20 Max VS rate 1 0m s 2 VS target 2 5m s Turn comp 0 2 Roll rate gain 2 0 Table 14 A22 A32 PID values Parameter Pitch VS Roll Heading P term 1 9 0 020 0 45 0 45 I term 5...

Page 52: ...eter Pitch VS Roll Heading P term 0 8 0 014 0 6 0 6 I term 6 5 12 0 4 5 26 0 D term 0 44 0 10 0 04 0 10 B 9 Comco Ikarus Table 17 C 42C configuration parameters Max arm mv 30 Max pitch rate 3 s Pitch target 10 Max roll rate 3 s Roll target 15 Max VS rate 1 0m s 2 VS target 2 5m s Turn comp 0 2 Roll rate gain 1 8 Table 18 C 42C PID values Parameter Pitch VS Roll Heading P term 1 1 0 016 0 85 0 5 I ...

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