(1) I think that one can come up with a reasonable emergency cutout relay setup, but, as Roboteq points out, one should also monitor for fused contacts. I don't think that open contacts are a problem; the chair just won't go. Fused contacts, however, would mean driving with no protection. So, what we have to do is check this before allowing driving. A script could trip the cutoff and set the motors to stop at startup, then we could use a digital input to check for voltage on the output of the relay, and if there is none then allow the relay to close and take the motors out of stop mode. Some programming needed, but should be doable.
Why 2 outputs for brakes (default Roboteq setting)? Each digital output is 1A max. 2 brakes in parallel is pushing it.
Just move the stick a bit? No stick for Rachi - head switch array and very low throttle settings indoors.
Use the internal current measure? Internal measure is inaccurate at low throttle, and Rachi drives at very low throttle, e.g. indoors 7% of maximum speed.
Relay contacts don't fuse, SSRs don't fail closed? Then why does Roboteq recommend independent monitoring for this, and why does Dynamic provide it? A failure of the digital out pin to which the relay is wired would give a "stuck closed" state too - and that was the failure on the Dynamic PM that I just replaced - relay OK, but the computer was telling it to close.
I did, however, realize that two actuators can be controlled with 3, rather than 4, outputs - Actuator 1 enable, Actuator 2 enable, and Reverse to trigger DPDT relays for both.
Ciao,
Lenny
Burgerman wrote:Use the internal current measure? Internal measure is inaccurate at low throttle, and Rachi drives at very low throttle, e.g. indoors 7% of maximum speed.
Why do you think this? It seems super accurate on the graphs, 1 percent is easy to see. And even radio control input has greater than 2048 resolution. 7 percent is huge. And may result in 30 or so percent percent motor current depending on impedance, battery voltage, flyback effect..
The torque mode uses the Motor Amps and not the Battery Amps. See “Battery Current
vs. Motor Current” on page 26. In all Roboteq controllers except the Separate Excitation
models, Battery Amps is measured and Motor Amps is estimated. The estimation is fairly
accurate at power level of 20% and higher. Its accuracy drops below 20% of PWM output
and no motor current is measured at all when the power output level is 0%, even though
current may be flowing in the motor, as it would be the case if the motor is pushed. The
torque mode will therefore not operate with good precision at low power output levels.
Furthermore the resolution of the amps capture is limited to around 0.5% of the full range.
On high current controller models, for example, amps are measured with 500mA increments.
If the amps limit is set to 100A, this means the torque will be adjustable with a
0.5% resolution. If on the same large controller the amps limit is changed to 10A, the
torque will be adjustable with the same 500mA granularity which will result in 5% resolution.
For best results use an amps limit that is at least 50% than the controller's max rating.
Given that Rachi needs the motor comp at very low currents, e.g. 7% of 60 Amp, I think the external current sensors at ca. Euro4 each are reasonable, it also means one doesn't have to program a reverse response to the Roboteq's current measurement to get positive feedback, just have to turn the sensor around and then use the PID settings. It may be the case that, after the first time someone does this, only P would need to be changed for different motors - it's a proportionately factor that should be much like the one calculated from motor resistance on mobility controllers.The torque mode uses the Motor Amps and not the Battery Amps. See “Battery Current
vs. Motor Current” on page 26. In all Roboteq controllers except the Separate Excitation
models, Battery Amps is measured and Motor Amps is estimated. The estimation is fairly
accurate at power level of 20% and higher. Its accuracy drops below 20% of PWM output
and no motor current is measured at all when the power output level is 0%, even though
current may be flowing in the motor, as it would be the case if the motor is pushed. The
torque mode will therefore not operate with good precision at low power output levels.
Furthermore the resolution of the amps capture is limited to around 0.5% of the full range.
On high current controller models, for example, amps are measured with 500mA increments.
If the amps limit is set to 100A, this means the torque will be adjustable with a
0.5% resolution. If on the same large controller the amps limit is changed to 10A, the
torque will be adjustable with the same 500mA granularity which will result in 5% resolution.
For best results use an amps limit that is at least 50% than the controller's max rating(emphasis added)
They do but its statistically very unlikely for 2 separate solid state systems to fail shorted. Normally they fail open. But its another safeguard, so the Roboteq would have to fail shorted as well as the safety device at the same time. Its possible I agree, but its not very likely.
The first sentence implies that "mixer" is applied BEFORE setting CIA's value, but the last sentence doesn't include "mixer" in the list of "adjustments". If "mixer" is applied before getting CIA, then adjusting forward/reverse speeds and adding motor compensation is simple. If "mixer" is applied after CIA is calculated, we have a bit more of a problem because we will have to do our own mixing (instead of using Roboteq's) before modifying the result of that to get the values to be sent to the motors. John, with mixing specified is it possible to watch the two Analog Command (or pulse, or serial) values with the GUI Roboteq software as you move the joystick? Do they follow just one or the other joystick axis or do they follow what you expect the motor to be doing? In other words, if you push the stick forward, do both channel's CIA increase (mixing before calculation of CIA) or does only one (mixing after calculation of CIA)?CIA - Read Internal Analog Command
Returns the motor command value that is computed from the Analog inputs whether or
not the command is actually applied to the motor. This query can be used, for example, to
read the command joystick from within a MicroBasic script or from an external microcomputer,
even though the controller may be currently responding to RS232 or Pulse command
because of a higher priority setting. The returned value is the raw Analog input value with
all the adjustments performed to convert it to a command (Min/Max/Center/Deadband/Linearity).
Syntax: ?CIA
Reply: CIA=nn
Where: nn = command value in +/-1000 range
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