Article: Why Position Beats Time. Slowdown Zones Held to the Millimetre.
Why Position Beats Time. Slowdown Zones Held to the Millimetre.
Why Position Beats Time.
Slowdown Zones Held to the Millimetre.
How native encoder feedback eliminates the slowdown drift that defines time-based gate automation, and what that gives the installer over the life of the operator.
If you've read Inside a Roger Brushless Motor and Four Parameters, Not One, you already know how Roger measures torque. The next architectural question is how it measures position — because everything the operator does at the ends of travel, from slowdown to stopping to reversal distance, depends on the controller knowing where the gate is, not just how long it has been moving.
The Prediction That Walks
Most conventional gate automation operates on a simple time-and-trip model. The controller starts a timer when the gate begins moving and watches for a mechanical limit switch to trip at the end of travel. Slowdown — the deceleration phase before the endstop — is initiated a set number of seconds before the expected limit trip, based on the motor's known characteristic speed.
The model works under stable conditions. The problem is that stable conditions don't exist at a gate over its working life.
Each variable shifts the actual time the gate takes to reach a given position. The timer's prediction of when slowdown should start walks out of alignment with the gate's real position. The slowdown begins too early and the gate creeps the last metre, or too late and it hits the endstop at speed.
“This is why time-based operators get re-tuning callouts seasonally. The mechanism doesn't fail — it just drifts.”
The Motor Reports Its Own Position
Every Roger brushless operator includes integrated position feedback from the motor itself. There are two implementations, depending on the operator family.
The controller infers rotor position from the back-EMF generated by the spinning permanent magnets on the undriven coils, between PWM switching events. The motor's own electromagnetic signature is read by the DSP and converted to a rotor angle.
The motor is its own position sensor. No additional wiring, no separate encoder cable.
Where higher precision is required, Roger fits a contactless magnetic encoder resolving rotor position to 4,096 pulses per revolution — angular resolution finer than 0.1° at the motor shaft.
At the gate leaf, after gearing, position is known to a fraction of a millimetre on a slider and a fraction of a degree on a swing.
Either way, the controller knows exactly where the gate is at every instant — independent of speed, temperature, battery state or wear.
Four Things Change at the Ends of Travel
“Begin slowdown 200mm before the closed position” means 200mm, every cycle, forever. There is no drift mechanism, because the trigger is not a timer — it is a position the controller measured directly.
Position-based stopping removes the need for mechanical cam-and-microswitch limit assemblies on most installations. The controller stops the gate at a position stored in its memory, not when an external switch trips.
The Roger commissioning routine runs the gate end-to-end once and stores the full travel as a position range. From then on the controller works inside known boundaries, with every parameter set against measured positions rather than estimated times.
As covered in Part 01, a reversal distance of 200mm means 200mm — not “approximately 200mm at room temperature on a fresh battery.” Position feedback is what makes that guarantee technically deliverable.
The Pit Is Where Switches Go to Fail
Underground installations expose the limitations of mechanical limit switches most clearly. The switches sit in the pit, exposed to moisture and contamination. Adjustment requires opening the pit. Failure means opening the pit. Every additional mechanical or electrical component in an underground enclosure is a future service call waiting for water to find it.
Eliminating the mechanical limit switch, by giving the controller direct position knowledge, removes one of the most common service failure modes on underground operators. The Roger range of underground operators is engineered specifically around this advantage.
The component that cannot fail in the pit is the one that was never installed there. Position feedback removes the limit switch from the enclosure entirely.
Four Outcomes in the Field
Every cycle, every season, for the life of the operator. No seasonal re-tuning, no apologetic callbacks.
The auto-programming routine takes minutes, not hours of trial-and-error timer adjustment.
Fewer mechanical components in the pit means fewer long-term failure modes.
Behaviour holds because it is measured digitally and stored digitally, not estimated from a timer that drifts. That is the architectural foundation of the long warranty cover Roger and Edgesmith offer on the brushless range.
Measured, Not Predicted
Time-based gate automation predicts where the gate is from how long it has been moving. The prediction is good enough most of the time, and it drifts with every variable that affects motor speed. Position-based control measures where the gate actually is, every instant, regardless of conditions.
Roger built native encoder feedback into every brushless operator because everything the controller does at the ends of travel depends on knowing position — not time.
The Callback You Never Get.
Drift is an easy thing to sell against, because every installer has taken the call. The gate was commissioned properly. Nothing failed. Six months later it is arriving at the endstop too fast, and the customer wants to know why.
The answer has never been workmanship. It is architectural: a timer cannot know where a gate is, so its prediction moves as conditions move. Position feedback removes the prediction entirely, and with it the whole class of service visit that comes from it.
We don't simply resell a brand. We choose components we can stand behind technically, and we explain them properly so installers and specifiers can make informed decisions. We distribute engineering, not motors.
— The Edgesmith Team
Part 03 — How Programmable Motion Curves Save the Gate Itself. Soft start, soft stop, electronic braking, and what they do to the structural life of welds, hinges and gearboxes.