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Thanks for the good interaction via comments to your question in order to better understand the working conditions and desired behavior of your proposed control circuit.

Here is a simple implementation of ESC_in=5 volts * %V_{limit} * %R₁ as we discussed via comments:

^{simulate this circuit – Schematic created using CircuitLab}

One very important detail is that whatever I add should not be able to generate a phantom signal, i.e. Vout MUST be always less or equal to Vin, even in the event of software bugs and reasonable hardware failures.

It certainly meets this requirement. The only failure mode is if V_limit has the possibility of exceeding 5 volts.

A potential disadvantage of this circuit is that the operator control range rescales. But since the operator's feedback is sensory, this may have minimal impact, particularly if you can ramp in your V_limit control voltage via your ADC.

Another version of this would be to take the wiper output of the pot, resistively scale it if necessary, and then use that as the V_ref for the ADC. You can also add common mode decoupled buffers as necessary to ensure low noise inputs throughout.

Thanks for the good interaction via comments to your question in order to better understand the working conditions and desired behavior of your proposed control circuit.

Here is a simple implementation of ESC_in=5 volts * %V_{limit} * %R₁ as we discussed via comments:

^{simulate this circuit – Schematic created using CircuitLab}

One very important detail is that whatever I add should not be able to generate a phantom signal, i.e. Vout MUST be always less or equal to Vin, even in the event of software bugs and reasonable hardware failures.

It certainly meets this requirement. The only failure mode is if V_limit has the possibility of exceeding 5 volts.

A potential disadvantage of this circuit is that the operator control range rescales. But since the operator's feedback is sensory, this may have minimal impact, particularly if you can ramp in your V_limit control voltage via your DAC.

Another version of this would be to take the wiper output of the pot, resistively scale it if necessary, and then use that as the V_ref for the DAC. You can also add common mode decoupled buffers as necessary to ensure low noise inputs throughout.

This seems painfully simple so I am probably overlooking something but I will give it a try in order to further illuminate the design requirements:

^{simulate this circuit – Schematic created using CircuitLab}

One very important detail is that whatever I add should not be able to generate a phantom signal, i.e. Vout MUST be always less or equal to Vin, even in the event of software bugs and reasonable hardware failures.

It certainly meets this requirement. The only failure mode is if V_limit has the possibility of exceeding 5 volts.

A potential disadvantage of this circuit is that the operator control range rescales. Whether or not this is significant depends upon the type of feedback used by the operator e.g. sensory feedback vs dial set point. This also goes to the question I asked in comments regarding the rate of change of V_limit and a better description of the application.

Thanks for the good interaction via comments to your question in order to better understand the working conditions and desired behavior of your proposed control circuit.

Here is a simple implementation of ESC_in=5 volts * %V_{limit} * %R₁ as we discussed via comments:

^{simulate this circuit – Schematic created using CircuitLab}

One very important detail is that whatever I add should not be able to generate a phantom signal, i.e. Vout MUST be always less or equal to Vin, even in the event of software bugs and reasonable hardware failures.

It certainly meets this requirement. The only failure mode is if V_limit has the possibility of exceeding 5 volts.

A potential disadvantage of this circuit is that the operator control range rescales. But since the operator's feedback is sensory, this may have minimal impact, particularly if you can ramp in your V_limit control voltage via your ADC.

Another version of this would be to take the wiper output of the pot, resistively scale it if necessary, and then use that as the V_ref for the ADC. You can also add common mode decoupled buffers as necessary to ensure low noise inputs throughout.

This seems painfully simple so I am probably overlooking something but I will give it a try in order to further illuminate the design requirements:

^{simulate this circuit – Schematic created using CircuitLab}

A potential disadvantage of this circuit is that the operator control range rescales. Whether or not this is significant depends upon the type of feedback used by the operator e.g. sensory feedback vs dial set point.

This seems painfully simple so I am probably overlooking something but I will give it a try in order to further illuminate the design requirements:

^{simulate this circuit – Schematic created using CircuitLab}

One very important detail is that whatever I add should not be able to generate a phantom signal, i.e. Vout MUST be always less or equal to Vin, even in the event of software bugs and reasonable hardware failures.

It certainly meets this requirement. The only failure mode is if V_limit has the possibility of exceeding 5 volts.

A potential disadvantage of this circuit is that the operator control range rescales. Whether or not this is significant depends upon the type of feedback used by the operator e.g. sensory feedback vs dial set point. This also goes to the question I asked in comments regarding the rate of change of V_limit and a better description of the application.