16F88 vs. 16LF88?

[Nigel Goodwin]

I get your point, but 10K might be exaggerating (i.e. under) a bit. The goal for the speed of the trombone robot was to have it capable of moving the slide as fast and as accurately as a professional trombone player. That means moving the slide between any consecutive semitones with a rhythm of sixteenth notes at a tempo of 150bpm. And that's just moving the slide, not stopping it for notes! So already we're talking on the scale of 1KHz, and we haven't even taken into account the time it will take to calculate for PID at any given moment in any given situation (i.e. how fast, how far, for how long the slide is moving), or the programming that will eventually be required to coordinate the slide movement with air and articulation in the rest of the robot.

Mechanical movement is slow, but not when it comes to emulating the capabilities of the human body. Do I really need to explain that to a Martial Artist?

It's still pitifully slow when compared with how fast PIC's run!

A PIC running at 4MHz executes 1,000,000 instructions per second, only 1uS per instruction - at 20MHz it's only 200nS per instruction.

I like to think I'm fast (but my teenage daughter is considerably faster! - damn her! ) but you're looking in the tens of mS for the absolutely fastest actions.

You'll find that when interfacing PIC's to mechanical systems that the VAST majority of it's time will be taken up just waiting for something mechanical to happen.

 

[Hank Fletcher]

Point taken, and I suppose in a way it's good to know that the resources as far as the mcu's concerned will not likely be deficient. My point, however, is that I think it's folly to presume that 10 or 20 MHz of 8-bit processing will ever be capable of the complex motor feedback (if you can call that) of humans. I mean, even if I can use a PIC to move the trombone slide, a human is doing it while accommodating all aspects of context (how loud the orchestra is playing on that occassion, for instance), and even anticipating things like turning over a page of music (a simple motor task that my robot won't be able to do). And a human can pack up the trombone and drive himself home at the end of the day! I can't see that happening with a PIC, despite my amazement at what they can do.

My real point is that the human mind and body is an amazing combination of motor and processing power that tends to be discounted. That is, until someone injures their arm and can't use it for a week - then they appreciate the value in human motor control.

 

[Nigel Goodwin]

My real point is that the human mind and body is an amazing combination of motor and processing power that tends to be discounted. That is, until someone injures their arm and can't use it for a week - then they appreciate the value in human motor control.

Yes, truely amazing, but still incredibly slow - even instructions from the brain to muscles take an incredibly long time to arrive - which is why reflexes can be much faster (but still thousands of times slower than a PIC).

 

[Hank Fletcher]

...instructions from the brain to muscles take an incredibly long time to arrive...

I'm not sure about that. My impression was in current medical thinking the nervous and muscular systems interacted in a sort of chemical reaction, meaning reactions to stimulation are arguably instantaneous (reflexes or not). When making comparisons between computers and people I think we'd be better to remember that we're comparing apples and oranges. Computers were designed the way they are because they were the best humans could think of, and are not the way they are because they emulate the best of what humans can do. Humans don't need to have a CPU, and I'd be surprised to find out we'd survived as long as we have if we did. Rather, body parts are capable of simultaneously reacting both autonomously, as part of the collective whole, and under the direction of conscious reasoning.

Our capability to do and think about things is only out-amazed by that seemingly unique human trait, our ability to learn. It wasn't until this past year that I started to be blown away by the non-literal means through which students learn. I think I'd grown up being a very literal learner (at least I thought I was, although looking back I know I had many non-literal opportunities that I explored), but now I believe the biggest mistake in education systems is presuming that that's the best way for humans to learn. It's not - it just happens to be the easiest way to compare successes and failures in education systems (which is why standardized tests tend to focus on extreme literacy, i.e. math and language studies). My point is, the best computers are still along way off being able to emulate human reasoning and muscular capabilities, and even further away from being able to teach themselves new tricks.

A trombonist can move a slide using an incredible amount of force, and through a variety of feedback control move that slide extremely quickly to a very accurate position. Oh yeah, and did I mention that he can do it all without barely making a sound?