background image

Figure 2.11: FFT of desired and measured acceleration along x-axis after running Northridge earthquake

4. In both the

fft_eval_pos.m

and

fft_eval_acc.m

scripts, you can adjust the frequency range by adjusting the

f_min

and

f_max

variables:

% min/max frequencies for plotting (Hz)

f_min = 1;

f_max = 10;

2.8

HEXAPOD CONTROLLERS

This section briefly describes some of the blocks used the Simulink models that are supplied with Hexapod, to be
used with QUARC. Some of the blocks designed specifically for the Hexapod are found in the

Hexapod_Library

Simulink library, depicted in Figure 2.12.

HEXAPOD Laboratory Guide

16

Summary of Contents for 6 DOF Hexapod

Page 1: ...6 DOF Hexapod Laboratory Guide Hexapod Quanser Inc 2016...

Page 2: ...com This document and the software described in it are provided subject to a license agreement Neither the software nor this document may be used or copied except as specified under the terms of that...

Page 3: ...l 9 2 5 Brake Bypass 12 2 6 Earthquake 13 2 7 FFT Analysis 15 2 8 Hexapod Controllers 16 3 Background 23 3 1 Modeling 23 3 2 Position Controller Design 23 3 3 Downloading New Earthquakes 24 4 System R...

Page 4: ...troke position Running joint level and world space position controls on the 6 DOF Hexapod Transfer function model of the linear actuator PID based controller used to control position of stage Prerequi...

Page 5: ...e supplied controllers are already configured for the hexapod2_usb data acquisition DAQ device If you are using these files on different DAQ or system then see the QUARC User Manual 1 for instructions...

Page 6: ...ch to the ON position 6 Run the QUARC controller by going to QUARC Start Each of the base joints should move to their limits until the limit switches are triggered Caution PRESS DOWN on the RED BUTTON...

Page 7: ...5 Click on QUARC Build to generate the controller 6 Run the QUARC controller by going to QUARC Start The upper stage should move to the HOME position when are all the linear actuator are in the mid st...

Page 8: ...their values in order to apply a sine wave command a HOME reference command b Sine or square wave position commands Figure 2 4 Hexapod position commands Caution Make sure the Hexapod is at the HOME p...

Page 9: ...is stopped However because this is performed after the controller is stopped it does not physically move the platform back to HOME This must be done manually as the controller is still running 10 Cli...

Page 10: ...on Reference subsystem block shown in Figure 2 6 The setpoint for each of the end effector s axes X Y Z Pitch Roll and Yaw can be set to either a sine wave or square wave Set the amplitude and frequen...

Page 11: ...te the controller 6 Run the QUARC controller by going to QUARC Start 7 Change the values of the Slider Gain blocks in the Desired Position Reference block shown in Figure 2 6 subsystem gradually to be...

Page 12: ...the World Position mm display block The measured joint positions are shown in the Joint Position display 2 5 BRAKE BYPASS The Hexapod_Brake_Bypass mdl model shown in Figure 2 7 allows the joints to b...

Page 13: ...l earthquake occurred can be scaled down and ran on the Hexapod Four historical earthquakes have been supplied for the user Northridge Kobe El Centro and Mendocino For instructions on how to download...

Page 14: ...nd cuts off the DC motor power 7 Typical position and acceleration responses when running the Northridge earthquake is shown in Figure 2 9 for the x axis a Position along X Axis b Measured Acceleratio...

Page 15: ...ng the Hexapod_Earthquake mdl QUARC controller as described in Sec tion 2 6 After Hexapod_Earthquake mdl is ran the commanded and measured position and acceleration data are automatically saved to the...

Page 16: ...sting the f_min and f_max variables min max frequencies for plotting Hz f_min 1 f_max 10 2 8 HEXAPOD CONTROLLERS This section briefly describes some of the blocks used the Simulink models that are sup...

Page 17: ...position of each joint the initial joint po sitions as well as the maximum allowed speed for each joint The block then outputs a calculated trajectory for each joint to follow This trajectory is the...

Page 18: ...caused by the desired position references between the links and the mounting brackets at each joint location The desired position references will be passed through the Joint Collision Avoidance subsy...

Page 19: ...if a fault occurs and the encoder velocities Using the Timebase block forces the controller to use the clock from the data acquisition device for more deterministic sampling when running the controlle...

Page 20: ...o reach the desired position denoted as F this subsystem computes the current required for the amplifier drives see Section 3 2 for the force to current conversion The current is converted to the PWM...

Page 21: ...effector position X Y Z Roll Pitch Yaw from the six joint positions q and the leg lengths It also the rotation matrix R Inverse kinematics calculates the six joint positions from the world coordinate...

Page 22: ...r desired position The axis to be displayed on the scope X Y Z Roll Pitch or Yaw can be selected using the Position Index block values between 0 and 5 The measured position commands are generated by t...

Page 23: ...structure F t kp qd t q t ki Z qd t q t dt kd q d t q t 3 2 where kp is the proportional control gain ki is the integral gain kd is the derivative control gain qd t 6 is the setpoint or reference join...

Page 24: ...se site On the PEER website each earthquake has various measurement stations and each station contains recorded displacement velocity and acceleration data of the tremor at different directions The de...

Page 25: ...record contains the measured acceleration for three different direction NGA_no_1105_HIK000 AT2 NGA_no_1105_HIK090 AT2 and NGA_no_1105_HIK UP AT2 9 To use NGA_no_1105_HIK000 AT2 go to make_quake_xyz m...

Page 26: ...s of MS VS and Matlabr are compatible with your version of QUARC and for what operating system Required Hardware Quanser 6 DOF Hexapod Note already includes integrated amplifier and data acquisition D...

Page 27: ...each axis and vary the amplitude and frequency of each Table 4 1 Files supplied with the 6 DOF Hexapod File Name Description q_scale p Produces a scaled position trajectory given desired acceleration...

Page 28: ...Hexapod CD 3 Open the setup_hexapod m script shown below Quanser s Hexapod Parameters Definition CAUTION DO NOT EDIT THIS FILE Otherwise Hexapod might not function properly clear all Mechanical Param...

Page 29: ...s for enable disable motors MOTOR_ENABLE_MASK 0 1 MOTOR_DISABLE_MASK 1 1 Maximum setpoint velocity and acceleration Max Joint Speed Software m s QDOT_MAX 0 65 Max Joint Acceleration Software m s 2 QDD...

Page 30: ...n the make_quake_xyz m script 4 Set the input_filename_x and input_filename_y variables in the script to the name of the earthquake file that is to be replayed on the shake table As shown below set th...

Page 31: ...tual recorded acceleration of the earthquake a 6 After running make_quake_xyz m with the files NGA_no_1806_SYL090 AT2 NGA_no_1806_SYL360 AT2 and NGA_no_1806_SYL UP AT2 at x_max 2 5 cm the following ou...

Page 32: ...y is compressed from 39 98 to 15 37 seconds 7 Once the script is ran the make_quake_xyz m Simulink Model can be used to replay the earthquake on the 6 DOF Hexapod See Section 2 6 for the procedure to...

Page 33: ...ES 1 Quanser Inc QUARC User Manual 2 Quanser Inc Quanser 6 DOF Hexapod User Manual 2016 3 Quanser Inc QUARC Compatibility Table 2016 4 Quanser Inc QUARC Installation Guide 2016 HEXAPOD Laboratory Guid...

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