Talk:Servomechanisms (aka "Servos") - Revision history

StefanoCapelli at 13:19, 27 January 2011

2011-01-27T13:19:07Z

StefanoCapelli at 13:11, 27 January 2011

2011-01-27T13:11:42Z

StefanoCapelli at 19:32, 26 January 2011

2011-01-26T19:32:39Z

StefanoCapelli at 19:30, 26 January 2011

2011-01-26T19:30:13Z

StefanoCapelli at 19:26, 26 January 2011

2011-01-26T19:26:00Z

StefanoCapelli at 19:25, 26 January 2011

2011-01-26T19:25:27Z

StefanoCapelli at 19:17, 26 January 2011

2011-01-26T19:17:25Z

StefanoCapelli at 19:00, 26 January 2011

2011-01-26T19:00:11Z

StefanoCapelli at 18:27, 26 January 2011

2011-01-26T18:27:21Z

StefanoCapelli at 18:12, 26 January 2011

2011-01-26T18:12:38Z

@@ Line 26: / Line 26: @@
 mounted a horn (the red one in the image) on the shaft, then attached a wire at a known distance from the horn's center, using the farthest hole available on the horn.  The wire's end will be used to apply a force, which, using the horn as the lever's arm, will create the desired moment on the shaft
 </li><li>
-arranged some objects (like bottles filled with water, wired together) with adjustable mass: their weight multiplied by the length of the winch's arm (19mm in our case) will equal the tested torque.</li></ul>
+arranged some objects (like bottles filled with water, wired together) with adjustable mass: their weight multiplied by the length of the winch's arm (19mm in our case) will equal the tested torque.</li>
 ''And we have assumed that:''

@@ Line 44: / Line 44: @@
 Motion degradation:  significantly slower, but still effective to rotate and lift the weight<br>
-On the temperature chart we see that the servo heating looks normal only during the first five minutes, and since the final motion degradation in not acceptable, we decide to reduce the applied torque.
+On the temperature chart (below, yellow line) we see that the servo heating looks normal only during the first five minutes, and since the final motion degradation in not acceptable, we decide to reduce the applied torque.
 At the same time we redefine our testing procedure:
-<ul><li>we want to use something stable for keeping the servo in place during our test, like a bench vice - so we mount our servo on its support, which we have previously attached on a Item basic profile.
+<ul><li>we want to use something stable for keeping the servo in place during our test, like a bench vice - so we mount our servo on its support (the one in use on E-2?), which we have previously attached on a Item 5 series profile.
 This way we can use the bench vice of AIRLab to make the Item profile and everything stand still (instead of holding it manually on the table's edge) so we can focus on the testing activity</li>
-<li>we use a lower force, by adopting a shorter arm, the one in the image, which has the advantage of not interfering with the cord during operations<br>[[Image:Servo_arm_148SH.jpg]]<br></li>
+<li>we use a lower torque by reducing the arm's length, and we adopt a new horn (the one in the image) which does not interfere with the cord that holds the weight, during shaft operations<br>[[Image:Servo_arm_148SH.jpg]]<br>&nbsp;</li>
 <li>we operate the servo during the first test like in the previous run:  making the arm stand still in the horizontal position, to achieve the maximum torque, then at the end of the test we go down and up again</li>
 <li>we do the second test applying continuously this pattern of movements:
@@ Line 66: / Line 66: @@
 We can accept this new estimate, given the premises above regarding the continuous torque, and it's interesting to point out that this torque equals the 49% of the stall torque declared on the box of the servo.

@@ Line 61: / Line 61: @@
 We've had these same results for both the test runs:
-Torque applied:  46.73 kgf*mm<br>
+Torque applied:  '''46.73 kgf*mm'''<br>
 Final temperature: 41 °C<br>
 Motion degradation:  reasonably slower<br>
 We can accept this new estimate, given the premises above regarding the continuous torque, and it's interesting to point out that this torque equals the 49% of the stall torque declared on the box of the servo.

@@ Line 40: / Line 40: @@
 We've set up our servo  for a new test run: this time we're using a lower torque, annotating the temperature, and trying to rotate the shaft at the end of our test, to see the difference in movement - the results:
-Torque applied:  59.19 kgf*mm
+Torque applied:  59.19 kgf*mm<br>
-Final temperature: 48 °C
+Final temperature: 48 °C<br>
-Motion degradation:  significantly slower, but still effective to rotate and lift the weight
+Motion degradation:  significantly slower, but still effective to rotate and lift the weight<br>
 On the temperature chart we see that the servo heating looks normal only during the first five minutes, and since the final motion degradation in not acceptable, we decide to reduce the applied torque.
@@ Line 61: / Line 61: @@
 We've had these same results for both the test runs:
-Torque applied:  46.73 kgf*mm
+Torque applied:  46.73 kgf*mm<br>
-Final temperature: 41 °C
+Final temperature: 41 °C<br>
-Motion degradation:  reasonably slower
+Motion degradation:  reasonably slower<br>
-We can accept this new assessment, given the premises above regarding the continuous torque, and it's interesting to point out that this torque is circa 49% of the stall torque declared on the box of the servo.
+We can accept this new estimate, given the premises above regarding the continuous torque, and it's interesting to point out that this torque equals the 49% of the stall torque declared on the box of the servo.

@@ Line 56: / Line 56: @@
 <li>5 up and down cycles, normal speed: period of approx. 3 seconds (2 second to go up, 1 second down)</li>
 <li>1 up and down cycle, quick</li>
-<li>10 seconds standing in a low stress position</li>
+<li>10 seconds standing in a low stress position</li></ul>
-<ul>
+</li></ul>
 </li>
 </ul>
 We've had these same results for both the test runs:

@@ Line 44: / Line 44: @@
 Motion degradation:  significantly slower, but still effective to rotate and lift the weight
-On the temperature chart we see that the servo heating seems normal during first five minutes.
+On the temperature chart we see that the servo heating looks normal only during the first five minutes, and since the final motion degradation in not acceptable, we decide to reduce the applied torque.
-Inspired by the movement at the end of this test run, we decide to adopt a new, more rigorous **, testing approach:
+At the same time we redefine our testing procedure:
-<ul><li>we want to use something stable for keeping the servo in place during our test, like a bench vice - so we mount our servo on its support **, which we have previously fixed on a Item element**.
+<ul><li>we want to use something stable for keeping the servo in place during our test, like a bench vice - so we mount our servo on its support, which we have previously attached on a Item element**.
-This way we can use our bench vice to hold the item element** still, instead of holding it on the table's edge, and we can focus on a more structured test</li>
+This way we can use the bench vice of AIRLab to hold the item element** still (instead of holding it manually on the table's edge) and we can focus on the testing activity</li>
-<li>we use a lower force, by adopting a shorter arm, via the arm of this image, which has the advantage of not interfering with the cord during lifting movements [[Image:Servo_arm_148SH.jpg]]<br></li>
+<li>we use a lower force, by adopting a shorter arm, the one in the image, which has the advantage of not interfering with the cord during lifting movements<br>[[Image:Servo_arm_148SH.jpg]]<br></li>
 <li>we do the first test making the arm stand still in the maximum torque position, as in the previous case, then at the end of the test we try to lift the weight</li>
 <li>we do the second test applying a continuous pattern of movements, so defined
@@ Line 60: / Line 60: @@
 </ul>
-We decide that there is a new kind of test
+We've had these same results for both the test runs:

@@ Line 15: / Line 15: @@
 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 [[Image:HITEC_HS-785HB.jpg]]<br>
 Here we describe how we've tried to assess the ''continuous torque'' of HS-645MG.
@@ Line 52: / Line 50: @@
 <ul><li>we want to use something stable for keeping the servo in place during our test, like a bench vice - so we mount our servo on its support **, which we have previously fixed on a Item element**.
 This way we can use our bench vice to hold the item element** still, instead of holding it on the table's edge, and we can focus on a more structured test</li>
-<li>we use a lower force, by adopting a shorter arm, via the arm of this image, which has the advantage of nor interfering with the movements</li>
+<li>we use a lower force, by adopting a shorter arm, via the arm of this image, which has the advantage of not interfering with the cord during lifting movements [[Image:Servo_arm_148SH.jpg]]<br></li>
-<li>we do the first test run normally</li>
+<li>we do the first test making the arm stand still in the maximum torque position, as in the previous case, then at the end of the test we try to lift the weight</li>
-<li>we do the second test run normally</li>
+<li>we do the second test applying a continuous pattern of movements, so defined
 </ul>
 We decide that there is a new kind of test

@@ Line 38: / Line 38: @@
 So we've started our test, using Hitec's specification of continuous torque (76.80 kgf*mm) as initial guess, and we've seen the measured temperature rising rapidly from 35° to 40° in the first three or four minutes of our test, so we've decided to abort this test, guessing that the actual temperature in the machinery/circuitry of our servo could be higher.
-We've prepared a second run with a lower torque (59.19 kgf*mm) and this time we've reached the same high temperature in 10 minutes, thereby deciding to adopt this second value as a better estimate of the "continuous" torque.
+We've prepared a second test run with a lower torque (59.19 kgf*mm) and this time we've reached the same high temperature in 10 minutes, thereby deciding to adopt this second value as a better estimate of the "continuous" torque.
-We've set up for a new run of our test, this time we're using a lower torque, annotating the temperature, and trying to rotate the shaft at the end of our test, to see the difference in movement - the results:
+We've set up our servo  for a new test run: this time we're using a lower torque, annotating the temperature, and trying to rotate the shaft at the end of our test, to see the difference in movement - the results:
 Torque applied:  59.19 kgf*mm
 Final temperature: 48 °C
-Motion degradation:  significantly slower, but still effective in lifting the weight
+Motion degradation:  significantly slower, but still effective to rotate and lift the weight
 On the temperature chart we see that the servo heating seems normal during first five minutes.