Re: [Emc-users] New stepper-servo --> Phase delay
They put a Cortex M0 on the module that sits on the board, along with the stepper driver and encoder. There's a greater latency inside the Cortex, it will likely have to respond to an interrupt thus have ISR latency. I presume they've got a PLL to prevent oscillation within the final step. It's not a bad case for an FPGA, since with proper coding the latency is limited by the response time of the transistors. Danny Nicklas Karlsson wrote: > Best option is probably to generate stepper signal from hardware timer. > > 2016-10-21 8:17 GMT+02:00 Danny Miller : > > > The SPI comm of course has latency within a comm period. > > > > However, the pulse output must be super-fast. It supports up to 14500 > > rpm, so if it's 2000steps/rev the whole step cycle is 2ms, realistically > > like maybe 1/4 of that for latency? > > > > Danny > > > > On 10/19/2016 11:34 PM, Nicklas Karlsson wrote: > > >>> ... The lag also seemed to vary with velocity. > > >>> > > >>> > > >> Most specifically, it was a lag in the encoder's loop to respond to > > >> acceleration. > > >> Velocity was fine, but when there is acceleration, the encoder's > > >> velocity didn't change for a few milliseconds, then it had to produce > > >> velocity greater than real for position to catch up. > > >> I thought it was a really severe problem, but it seems it may not be all > > >> that bad. But, it can make servo tuning more tricky. > > >> > > >> Jon > > > Delay is called phase in control theory and it is not good at all for > > fast response. > > > > > > > > -- > > > Check out the vibrant tech community on one of the world's most > > > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > > > ___ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > > -- > > Check out the vibrant tech community on one of the world's most > > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > > ___ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > -- > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] New stepper-servo --> Phase delay
Best option is probably to generate stepper signal from hardware timer. 2016-10-21 8:17 GMT+02:00 Danny Miller : > The SPI comm of course has latency within a comm period. > > However, the pulse output must be super-fast. It supports up to 14500 > rpm, so if it's 2000steps/rev the whole step cycle is 2ms, realistically > like maybe 1/4 of that for latency? > > Danny > > On 10/19/2016 11:34 PM, Nicklas Karlsson wrote: > >>> ... The lag also seemed to vary with velocity. > >>> > >>> > >> Most specifically, it was a lag in the encoder's loop to respond to > >> acceleration. > >> Velocity was fine, but when there is acceleration, the encoder's > >> velocity didn't change for a few milliseconds, then it had to produce > >> velocity greater than real for position to catch up. > >> I thought it was a really severe problem, but it seems it may not be all > >> that bad. But, it can make servo tuning more tricky. > >> > >> Jon > > Delay is called phase in control theory and it is not good at all for > fast response. > > > > > -- > > Check out the vibrant tech community on one of the world's most > > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > > ___ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > -- > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] New stepper-servo --> Phase delay
The SPI comm of course has latency within a comm period. However, the pulse output must be super-fast. It supports up to 14500 rpm, so if it's 2000steps/rev the whole step cycle is 2ms, realistically like maybe 1/4 of that for latency? Danny On 10/19/2016 11:34 PM, Nicklas Karlsson wrote: >>> ... The lag also seemed to vary with velocity. >>> >>> >> Most specifically, it was a lag in the encoder's loop to respond to >> acceleration. >> Velocity was fine, but when there is acceleration, the encoder's >> velocity didn't change for a few milliseconds, then it had to produce >> velocity greater than real for position to catch up. >> I thought it was a really severe problem, but it seems it may not be all >> that bad. But, it can make servo tuning more tricky. >> >> Jon > Delay is called phase in control theory and it is not good at all for fast > response. > > -- > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] New stepper-servo --> Phase delay
> > ... The lag also seemed to vary with velocity. > > > > > Most specifically, it was a lag in the encoder's loop to respond to > acceleration. > Velocity was fine, but when there is acceleration, the encoder's > velocity didn't change for a few milliseconds, then it had to produce > velocity greater than real for position to catch up. > I thought it was a really severe problem, but it seems it may not be all > that bad. But, it can make servo tuning more tricky. > > Jon Delay is called phase in control theory and it is not good at all for fast response. -- Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
