http://www.allaboutcircuits.com/projects-preview/36635
Dear author and reviewers,
Here are the results of my technical review. One purpose of this review is to facilitate discussion and input from other AAC contributors. If the reviewer community decides that a particular issue does not require revision, all the better—leave it as is. Any issues that are deemed significant enough to require revision should be addressed before the article is published.
If I have botched or missed anything, please bring me in front of the class and apply the dunce cap. That’s how I learn.
Thanks to all for your time and expertise.
I made a number of revisions and added a link to an existing article on PID theory. The following are remaining issues.
1. “Moreover, as the temperature changes, its internal winding resistance will also change; hence, it will not perform the same in two different environments.”
I don’t think that ambient temperature change with a motor is a good example of how a device will not exhibit consistent/predictable performance under varying conditions, for two reasons: 1) The winding is made of typical conductive material, presumably copper or aluminum, and we usually don’t worry about copper or aluminum wires exhibiting significant changes in resistance in response to ambient temperature changes. 2) Motors with high winding currents will experience heating from power dissipated inside the motor. I would say that this internal heat generation is far more significant than typical ambient temperature changes.
2. Re: Figure 1
The image includes some items that are not in the list. Do you want to modify the list so that it is consistent with the image? Also, is that steel/copper wool? What is that used for?
3. “A regular analogue DC servo will usually have an op-amp-based controller already contained within the casing”
I think it is safe to say that every servo will have a controller, since (in my experience) the integrated feedback control is a defining characteristic of a servomotor. But maybe only some of them use op-amps? Or have you come across a servo that does not include a controller?
4. Re: Table 1
You don’t need the degree symbol in the column header (i.e., next to “Rotation Relative to Centre”) because it is attached to each entry in the column. (This applies also to the right-hand column in Table 2; see comment #6.)
5. Re: Table 1 and Table 2
We should use “Pulse Width” instead of “Pulse Length” because this is the more standard term and because it is consistent with how we describe the servo’s control signal, i.e., pulse-width modulation.
6. Re: Table 2
The velocity information is a bit confusing. First, what is “proportional velocity”? Should that be “angular velocity”? Also, the typical unit for a velocity is distance per time (e.g., meters per second) or angle per time (e.g., radians per second), whereas the table uses seconds/angle. This unit becomes even more awkward when you have a negative sign, because now you are saying that the motor turns 60° in negative 0.14 seconds. And it becomes downright baffling when we see that the motor turns 60° in zero seconds! Would it be possible to change the table so that the velocity is given in degrees or rotations per second?
Dear author and reviewers,
Here are the results of my technical review. One purpose of this review is to facilitate discussion and input from other AAC contributors. If the reviewer community decides that a particular issue does not require revision, all the better—leave it as is. Any issues that are deemed significant enough to require revision should be addressed before the article is published.
If I have botched or missed anything, please bring me in front of the class and apply the dunce cap. That’s how I learn.
Thanks to all for your time and expertise.
I made a number of revisions and added a link to an existing article on PID theory. The following are remaining issues.
1. “Moreover, as the temperature changes, its internal winding resistance will also change; hence, it will not perform the same in two different environments.”
I don’t think that ambient temperature change with a motor is a good example of how a device will not exhibit consistent/predictable performance under varying conditions, for two reasons: 1) The winding is made of typical conductive material, presumably copper or aluminum, and we usually don’t worry about copper or aluminum wires exhibiting significant changes in resistance in response to ambient temperature changes. 2) Motors with high winding currents will experience heating from power dissipated inside the motor. I would say that this internal heat generation is far more significant than typical ambient temperature changes.
2. Re: Figure 1
The image includes some items that are not in the list. Do you want to modify the list so that it is consistent with the image? Also, is that steel/copper wool? What is that used for?
3. “A regular analogue DC servo will usually have an op-amp-based controller already contained within the casing”
I think it is safe to say that every servo will have a controller, since (in my experience) the integrated feedback control is a defining characteristic of a servomotor. But maybe only some of them use op-amps? Or have you come across a servo that does not include a controller?
4. Re: Table 1
You don’t need the degree symbol in the column header (i.e., next to “Rotation Relative to Centre”) because it is attached to each entry in the column. (This applies also to the right-hand column in Table 2; see comment #6.)
5. Re: Table 1 and Table 2
We should use “Pulse Width” instead of “Pulse Length” because this is the more standard term and because it is consistent with how we describe the servo’s control signal, i.e., pulse-width modulation.
6. Re: Table 2
The velocity information is a bit confusing. First, what is “proportional velocity”? Should that be “angular velocity”? Also, the typical unit for a velocity is distance per time (e.g., meters per second) or angle per time (e.g., radians per second), whereas the table uses seconds/angle. This unit becomes even more awkward when you have a negative sign, because now you are saying that the motor turns 60° in negative 0.14 seconds. And it becomes downright baffling when we see that the motor turns 60° in zero seconds! Would it be possible to change the table so that the velocity is given in degrees or rotations per second?