In Santa’s workshop, the gingerbread conveyor belt chugged along with the serenity of a sleigh ride on fresh snow, carrying neat rows of biscuits to the decorating station. This smooth operation was the merit of a Pinecone–Icicle (PI) controller (very similar to the Pinecone–Icicle–Dancing (PID) controller used for controlling the vapour pressure, see 16 December, but without the dancing elves) lovingly fine-tuned by Jingles, the industrious elf in charge of the factory floor.
But one particularly hectic morning, disaster struck. A rogue marshmallow — suspiciously oversized and almost certainly reindeer-related — fell into the conveyor mechanism and jammed it completely. No matter how hard the motor pushed, the belt simply refused to budge.
Jingles spotted the problem immediately, yanked out the marshmallow, and lobbed it into the nearest hot cocoa vat. The belt was free, but instead of gliding calmly back to its normal pace as expected, the conveyor suddenly sprang into action at full blast.
It took several seconds – an eternity for Jingles – to regain the correct speed. In the meantime biscuits went airborne, gumdrops ricocheted off the walls, and the frosting machines spun wildly out of control. The factory had turned into a chaotic winter wonderland.
Utterly bewildered, Jingles called an emergency meeting of the workshop’s finest minds. “Why didn’t the belt just return to its normal speed?” she asked, exasperated. “Once the marshmallow was out of the way it should have settled, not launched into biscuit bonanza!”
Everyone scratched their heads. Mitzy calmly sipped her tea. Grumbles mumbled incoherently. Squeezy stress-ate an entire candy cane, wrapper and all. And as for Trixie, she just raised an eyebrow with obvious glee: nothing delighted her more than a Jingles-led malfunction she didn’t have to fix, or said more clearly, a rare moment when the workshop’s golden child looked fallible.
After some embarrassing instants of silence, seeing that the head-scratching had reached its productive limit, Jingles declared, “All right, we’ll each think of a solution. Meet back here tomorrow. And remember: whatever you propose, we’ll need to file a funding request with the North-pole Institute for Confectionery Engineering. So, extra candies for catchy acronyms. You know how nice the NICE people are about their paperwork.” They all agreed – well, sort of.
The next day, the team reconvened. Everyone presented a proposal, and then the room went quiet: all that remained was the gentle hum of the now-behaving conveyor belt.
Below is a short transcript of the meeting. Who was right?
a. 🎭🩰⚙️ Trixie was first to speak, despite Jingles’ very clear request to wait her turn. She strutted forward, flipping her scroll open with dramatic flair. “As usual, I’ll start. My proposal is TWIRL: Tiny Wiggles to Improve Response Linearity. You see, Jingles never uses Dancing — just Pinecone and Icicle. I think not even the Grand Spirit of the Elves knows why. But without those little ‘D’ steps, everything gets jerky and wild. TWIRL lets the dancing elves step in when needed — to smooth out sudden jerks and keep everything elegant and well-paced. I’m confident it will work — graceful, stylish, and frankly, long overdue.”
b. 🍬📈🐻 Squeezy practically bounced out of his seat, waving his sticky napkin like a flag — still cleaning up from his latest candy cane, though thankfully he’d avoided the wrapper this time. “OK, guys, here’s mine. It’s GROWL: Gradual Regulation Of Weighty Loads. The problem isn’t how fast the belt runs, but how quickly it gets going. So, instead of fiddling with the Pinecone and Icicle, we simply ask the upstream candy machines to make the sweets a bit bigger when needed. Bigger candies mean heavier loads, which slow the belt down naturally — fewer flying biscuits, less chaos. Plus, the children will love it. Win–win!”
c. 🛑💪🔧 Grumbles stood, slowly and stiffly, with the air of someone about to announce something profoundly sensible. “That’s all a bit over the top, if you ask me. Let’s keep it simple. My proposal is BUMP: Bound Upon Motor Push. In a nutshell, we don’t touch the Pinecone Icicle at all, that’s fine, but also we do not try to explain to those harebrained guys up in the biscuit factory how to fiddle with weight control, for the Grand Spirit’s sake. We just limit the maximum torque that the motor’s allowed to use when it suddenly wakes up. You can’t go full throttle straight after a nap — trust me, I’ve tried. Can’t see why it shouldn’t work.”
d. 🍵📉🧠 At last, Mitzy stepped forward with a quiet smile, clutching a neatly folded page and a teacup. “Mine’s small, but I’m confident it’ll help. It’s PAIR: Pinecone-Aware Icicle Resizer. The problem is that when the motor gets stuck, the Icicle keeps growing — and it can’t melt instantly when the jam clears. It takes time, and that’s what leads to the temporary speed boost. PAIR keeps an eye on the Icicle and gently resizes it when it’s grown too big to be helpful. That way, the Pinecone and Icicle together always reflect what the motor is actually doing, and never ask it to do what it cannot.”
Related control theory topic: integrator windup