 | | "Servo" Driver for NQC —Iain Hendry
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| | | Hi All, I've got a bit of a problem! Whenever I do a cartesian (or other) robot model, I typically (in NQC) will program a "driver" which can spin the motors with the rotation sensors to any position and delecerate to finely reach the destination. (...) (23 years ago, 27-Jan-02, to lugnet.robotics)
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| | | | | Re: "Servo" Driver for NQC —Jerry Kalpin
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| | | | | (...) This is absolutely the right group! If you do searches on 'skipped counts' or similar wording you will find lots of posts on the rotation sensor missing counts at low speeds. And if you want to get to the bottom line quickly, check this (...) (23 years ago, 27-Jan-02, to lugnet.robotics)
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| | | | | | | Re: "Servo" Driver for NQC —Iain Hendry
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| | | | | | "Jerry Kalpin" <jdkalpin@sympatico.ca> wrote in message news:GqLv8t.12r@lugnet.com... (...) counts' (...) Well, I'm not really worried about missing a few counts (even though yeah, I've noticed that problem, and it's *extremly* irritating...). I was (...) (23 years ago, 27-Jan-02, to lugnet.robotics)
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| | | | | Re: "Servo" Driver for NQC —Stephen Edwards
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| | | | | Rebel Transcanner wrote: > (...) I take it you are really doing on...float...on...float cycles with your motor instead of using "off", which actually performs active braking (on/off cycles are almost guaranteed to give serious mechanical jitters). (...) (23 years ago, 29-Jan-02, to lugnet.robotics)
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| | | | | | | Re: "Servo" Driver for NQC —Iain Hendry
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| | | | | | | "Stephen Edwards" <lego-robotics@crynwr.com> wrote in message news:3C56AA4F.409050....vt.edu... (...) wait (...) Nope, I'm using Off, because I need to brake the motor to pulse it. Floating it does almost nothing - the inertia of the motor carries (...) (23 years ago, 29-Jan-02, to lugnet.robotics)
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| | | | | | | | | Re: "Servo" Driver for NQC —Steve Baker
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| | | | | | | | (...) I have to disagree with your approach. Even at low speeds, alternating between pushing on the gas and stamping on the brake isn't the way to drive smoothly. Perhaps you need to gear the machine differently and use less power during the ON (...) (23 years ago, 29-Jan-02, to lugnet.robotics)
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| | | | | | | | | | Re: "Servo" Driver for NQC —Iain Hendry
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| | | | | | | | "Steve Baker" <lego-robotics@crynwr.com> wrote in message news:3C56E677.33FD99...ail.net... (...) Floating (...) if (...) I cannot gear it differently - the geartrain is optimized for the correct speed I must achieve. Float doesn't work because of (...) (23 years ago, 30-Jan-02, to lugnet.robotics)
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| | | | | | | Re: "Servo" Driver for NQC —Dean Hystad
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| | | | | | The ON/OFF bang-bang control you are trying has some problems that proportional control does not. While it is true that if the update rate is high enough, or the controlled plant damped enough, that switching a drive ON and OFF can simulate (...) (23 years ago, 30-Jan-02, to lugnet.robotics)
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| | | | | Re: "Servo" Driver for NQC —Matthias Jetleb
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| | | | (...) Well I haven't seen your version of the Project-X design, but I'll assume it's similar (albeit vastly inferior) to the one I'm entering. I'm assuming that for the sake of speed, you are keeping moving mass to a minimum and hence, not loading (...) (23 years ago, 30-Jan-02, to lugnet.robotics)
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| | | | | | Re: "Servo" Driver for NQC —Steve Baker
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| | | | | (...) But it doesn't need to. The 'power' settings built into the RCX firmware are already using pulse-width modulation to adjust the amount of power the motor delivers. ---...--- Steve Baker ---...--- Mail : <sjbaker1@airmail.net> WorkMail: (...) (23 years ago, 29-Jan-02, to lugnet.robotics)
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| | | | | | | Re: "Servo" Driver for NQC —Iain Hendry
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| | | | | | | "Steve Baker" <lego-robotics@crynwr.com> wrote in message news:3C56F4B7.FC698E...ail.net... (...) Then why doesn't it work? :-/ At lower power settings, all it seems to do is sit there and humm, not wanting to go. It really dosen't work that well in (...) (23 years ago, 30-Jan-02, to lugnet.robotics)
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| | | | | | | Re: "Servo" Driver for NQC —Jerry Kalpin
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| | | | | | | (...) <snip> (...) Right, but in the firmware PWM, it is 'on-float-on-float' not 'on-brake-on-brake' I think (but I'm not sure). In fact, the 'on-brake-on-brake' is a neat way to get fine control to (say) just crack a pneumatic valve to move a (...) (23 years ago, 30-Jan-02, to lugnet.robotics)
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| | | | | | | | | Re: "Servo" Driver for NQC —Dick Swan
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| | | | | | | | This is a long post. It covers the following: 1. How the "WAIT x 10 msec" opcode is implemented and its inherent inaccuracy for low delays. And suggests an alternative code implementation 2. How RCX motor PWM is implemented. And the implication that (...) (23 years ago, 31-Jan-02, to lugnet.robotics)
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| | | | | | | | | | Re: "Servo" Driver for NQC —Jerry Kalpin
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| | | | | | | | | <snip> (...) <snip> (...) Really good post! Just a loose end: If you press the 'stop' button on the RCX while a motor is running the motor stops in the 'brake' condition. If you connect a spare motor to a gray battery box with the switch in a (...) (23 years ago, 31-Jan-02, to lugnet.robotics)
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| | | | | | | | | | Re: "Servo" Driver for NQC —Iain Hendry
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| | | | | | | | "Dick Swan" <dickswan@sbcglobal.net> wrote in message news:GqsAv4.GL1@lugnet.com... (...) <snip> Dick, let me first say thank you for the post. I've implemented some of your suggestions and my robot has gone from unuseable to operating as I had (...) (23 years ago, 1-Feb-02, to lugnet.robotics)
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| | | | | | | Re: "Servo" Driver for NQC —Matthias Jetleb
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| | | | | | (...) Yes, but only one of 8 settings (why not all 256??? I don't understand why they limited this). Sometimes only 8 settings doesn't give you enough finesse. Matthias Jetleb (23 years ago, 2-Feb-02, to lugnet.robotics)
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| | | | | | | | Re: "Servo" Driver for NQC —Steve Baker
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| | | | | | (...) That was explained earlier. They are using an 8 bit number to store the *pattern* of the modulation. With 8 bits, there are only 8 different ratios of 1's to 0's - and one of those is to have no power at all. Hence there are seven power (...) (23 years ago, 2-Feb-02, to lugnet.robotics)
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| | | | | | Re: "Servo" Driver for NQC —Iain Hendry
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| | | | "Matthias Jetleb" <Jetleb@Netcom.ca> wrote in message news:3c5763f6.195969...net.com... (...) Ooooooooo, someone else is actually NOT doing a gantry? ;) (...) The mass is at a minumum, but due to the size fo the robot to get the required work (...) (23 years ago, 30-Jan-02, to lugnet.robotics, lugnet.org.ca.rtltoronto)
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