On 4/24/2012 3:46 PM, upsidedown@downunder.com wrote:> On Tue, 24 Apr 2012 03:59:16 GMT, Al Clark<aclark@danvillesignal.com> > wrote: > >> >> As far as I know, Microchip does not have a floating point device. Generally >> speaking, floating point emulation is very inefficient with fixed point >> processors and more times than not, a bad idea if you care about performance. >> It's usually better to use a fixed point version of the function or migrate >> to a device with native floating point support. > > How many embedded applications really do any heavy floating point > operations ? > > OK, if you do a lot of floating point matrix multiplications and > inversions with large arrays, a real HW FP is a must. > > However, in most cases the need for floating point processing in the > embedded environment is simply due to constructs like > > sprintf (TextString, "Length %6.2f meters", Integer_cm_value/100.0) ; > > Thus, the total number of floating point instruction is typically very > low and not justify any FP HW. Of course, the emulation code needs > some space, so there are some tradeoffs to be made.Has anyone here designed or even seen a high-performance servo with an air-powered actuator? The compliance is usually a killer. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Floating Point DSP from Microchip (?)
Started by ●April 23, 2012
Reply by ●April 27, 20122012-04-27
Reply by ●April 27, 20122012-04-27
On 27 Apr., 06:36, Jerry Avins <j...@ieee.org> wrote:> On 4/24/2012 3:46 PM, upsided...@downunder.com wrote: > > > > > > > > > > > On Tue, 24 Apr 2012 03:59:16 GMT, Al Clark<acl...@danvillesignal.com> > > wrote: > > >> As far as I know, Microchip does not have a floating point device. Generally > >> speaking, floating point emulation is very inefficient with fixed point > >> processors and more times than not, a bad idea if you care about performance. > >> It's usually better to use a fixed point version of the function or migrate > >> to a device with native floating point support. > > > How many embedded applications really do any heavy floating point > > operations ? > > > OK, if you do a lot of floating point matrix multiplications and > > inversions with large arrays, a real HW FP is a must. > > > However, in most cases the need for floating point processing in the > > embedded environment is simply due to constructs like > > > sprintf (TextString, "Length %6.2f meters", Integer_cm_value/100.0) ; > > > Thus, the total number of floating point instruction is typically very > > low and not justify any FP HW. Of course, the emulation code needs > > some space, so there are some tradeoffs to be made. > > Has anyone here designed or even seen a high-performance servo with an > air-powered actuator? The compliance is usually a killer. >maybe it is doable: http://machinedesign.com/article/servocontrol-with-pneumatic-actuators-1011 though I'd expect it to be a bit like driving a car using a pair of rubber bands -Lasse
Reply by ●April 27, 20122012-04-27
On Fri, 27 Apr 2012 08:59:27 -0700 (PDT), "langwadt@fonz.dk" <langwadt@fonz.dk> wrote:>On 27 Apr., 06:36, Jerry Avins <j...@ieee.org> wrote: >> On 4/24/2012 3:46 PM, upsided...@downunder.com wrote: >> >> >> >> >> >> >> >> >> >> > On Tue, 24 Apr 2012 03:59:16 GMT, Al Clark<acl...@danvillesignal.com> >> > wrote: >> >> >> As far as I know, Microchip does not have a floating point device. Generally >> >> speaking, floating point emulation is very inefficient with fixed point >> >> processors and more times than not, a bad idea if you care about performance. >> >> It's usually better to use a fixed point version of the function or migrate >> >> to a device with native floating point support. >> >> > How many embedded applications really do any heavy floating point >> > operations ? >> >> > OK, if you do a lot of floating point matrix multiplications and >> > inversions with large arrays, a real HW FP is a must. >> >> > However, in most cases the need for floating point processing in the >> > embedded environment is simply due to constructs like >> >> > sprintf (TextString, "Length %6.2f meters", Integer_cm_value/100.0) ; >> >> > Thus, the total number of floating point instruction is typically very >> > low and not justify any FP HW. Of course, the emulation code needs >> > some space, so there are some tradeoffs to be made. >> >> Has anyone here designed or even seen a high-performance servo with an >> air-powered actuator? The compliance is usually a killer. >> > >maybe it is doable: http://machinedesign.com/article/servocontrol-with-pneumatic-actuators-1011 > >though I'd expect it to be a bit like driving a car using a pair of >rubber bands > > >-LasseMy 1962 Beech Bonanza (airplane) had a vacuum driven TACTAIR autopilot that was steady as bedrock. No electronics required. There is a lot of technology that has been abandoned. Way too many pilots out there on instruments that relied completely on the TACTAIR! John Ferrell W8CCW
Reply by ●April 28, 20122012-04-28
On 27.4.12 11:55 , John Ferrell wrote:> On Fri, 27 Apr 2012 08:59:27 -0700 (PDT), "langwadt@fonz.dk" > <langwadt@fonz.dk> wrote: > >> On 27 Apr., 06:36, Jerry Avins<j...@ieee.org> wrote: >>> On 4/24/2012 3:46 PM, upsided...@downunder.com wrote: >>> >>> >>> >>> >>> >>> >>> >>> >>> >>>> On Tue, 24 Apr 2012 03:59:16 GMT, Al Clark<acl...@danvillesignal.com> >>>> wrote: >>> >>>>> As far as I know, Microchip does not have a floating point device. Generally >>>>> speaking, floating point emulation is very inefficient with fixed point >>>>> processors and more times than not, a bad idea if you care about performance. >>>>> It's usually better to use a fixed point version of the function or migrate >>>>> to a device with native floating point support. >>> >>>> How many embedded applications really do any heavy floating point >>>> operations ? >>> >>>> OK, if you do a lot of floating point matrix multiplications and >>>> inversions with large arrays, a real HW FP is a must. >>> >>>> However, in most cases the need for floating point processing in the >>>> embedded environment is simply due to constructs like >>> >>>> sprintf (TextString, "Length %6.2f meters", Integer_cm_value/100.0) ; >>> >>>> Thus, the total number of floating point instruction is typically very >>>> low and not justify any FP HW. Of course, the emulation code needs >>>> some space, so there are some tradeoffs to be made. >>> >>> Has anyone here designed or even seen a high-performance servo with an >>> air-powered actuator? The compliance is usually a killer. >>> >> >> maybe it is doable: http://machinedesign.com/article/servocontrol-with-pneumatic-actuators-1011 >> >> though I'd expect it to be a bit like driving a car using a pair of >> rubber bands >> >> >> -Lasse > My 1962 Beech Bonanza (airplane) had a vacuum driven TACTAIR autopilot > that was steady as bedrock. No electronics required. There is a lot of > technology that has been abandoned. Way too many pilots out there on > instruments that relied completely on the TACTAIR! > John Ferrell W8CCWDid you have a second vacuum pump? -- Tauno Voipio OH2UG, flying a very electric airplane, DA42
Reply by ●April 29, 20122012-04-29
"langwadt@fonz.dk" wrote:> On 27 Apr., 06:36, Jerry Avins ?j...@ieee.org? wrote: > > ? Has anyone here designed or even seen a high-performance servo with an > ? air-powered actuator? The compliance is usually a killer. > ? > > maybe it is doable: http://machinedesign.com/article/servocontrol-with-pneumatic-actuators-1011 > > though I'd expect it to be a bit like driving a car using a pair of > rubber bandsI had a car in 70's that uses air logic and amplifiers in its engine controller. Gains were analog needle valves and I had two "incidents" where an air amp locked up and the car accelerated until the ignition was turned off with the key. In both cases it buried the tach almost instantly. That was the bad news, the good news was when it was properly set up it worked well. w..
Reply by ●April 30, 20122012-04-30
On Sat, 28 Apr 2012 11:36:30 +0300, Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:>On 27.4.12 11:55 , John Ferrell wrote: >> On Fri, 27 Apr 2012 08:59:27 -0700 (PDT), "langwadt@fonz.dk" >> <langwadt@fonz.dk> wrote: >>>>> maybe it is doable: http://machinedesign.com/article/servocontrol-with-pneumatic-actuators-1011 >>> >>> though I'd expect it to be a bit like driving a car using a pair of >>> rubber bands >>> >>> >>> -Lasse >> My 1962 Beech Bonanza (airplane) had a vacuum driven TACTAIR autopilot >> that was steady as bedrock. No electronics required. There is a lot of >> technology that has been abandoned. Way too many pilots out there on >> instruments that relied completely on the TACTAIR! >> John Ferrell W8CCW > >Did you have a second vacuum pump?I no longer own the airplane. It did not have a backup vacuum pump. The electronics and vacuum systems were each others backups. The point I was trying to make is that pneumatic systems can be constructed in a manner to be precise, robust and strong. Dirt & dust are the main problems encountered. John Ferrell W8CCW
Reply by ●April 30, 20122012-04-30
On 4/29/2012 7:30 PM, Walter Banks wrote:> > > "langwadt@fonz.dk" wrote: > >> On 27 Apr., 06:36, Jerry Avins ?j...@ieee.org? wrote: >> >> ? Has anyone here designed or even seen a high-performance servo with an >> ? air-powered actuator? The compliance is usually a killer. >> ? >> >> maybe it is doable: http://machinedesign.com/article/servocontrol-with-pneumatic-actuators-1011 >> >> though I'd expect it to be a bit like driving a car using a pair of >> rubber bands > > I had a car in 70's that uses air logic and amplifiers in its engine > controller. Gains were analog needle valves and I had two > "incidents" where an air amp locked up and the car accelerated > until the ignition was turned off with the key. In both cases it > buried the tach almost instantly. That was the bad news, the > good news was when it was properly set up it worked well.Power brakes are usually vacuum operated (at least they were when I first became acquainted with them). Pneumatics can work quite well when force is the controlled variable. I had position servos in mind when I asked the question. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
