CDR Controlled Magnetics — variable ratio and regenerative braking

Ratio control without clutches, bands, or belts

Two magnetic coil sets govern the second input to a sun-and-planet gear set. One pulls that input up to shaft speed; the other pulls it to a stop. Between them lies every ratio in the range — and, on deceleration, a path back to the battery.

Contact-free · no wear surfaces Continuous ratio · no shift event Regenerative · coils generate

01 — Ratio control

Two coils, one gear set

The input shaft drives the sun. The output leaves on the planet carrier. The ring is the second input — free to turn, and controlled entirely by the two coil sets. Drag the command slider and watch the ring speed carry the output ratio with it.

How to use it: Ratio command blends the two coils — 0% locks the ring to the housing for maximum torque multiplication, 100% locks it to the input for direct 1:1 drive, and everything between is a stiffened balance point. Input shaft speed sets the motor's rpm. Output load is how hard the output is being asked to work; push it up and the coils have to fight harder to hold the ring at its target speed, so the ring — and with it the output — slips back toward the housing, pushing the ratio up under load rather than down. Coil coupling strength is the magnetic field on both coils: weaker field means less authority, so the same load produces more slip. Ring / sun tooth ratio Z sets the gear set's spread — a higher Z widens the gap between the lowest and highest ratio the transmission can reach.

What it shows: the diagram animates the sun, ring, and carrier at their live speeds. The stat row reports input/ring/output rpm, the instantaneous ratio, the torque delivered at the output, and the power each coil is handling. The cards below walk through the three regimes — full ground, blended, and full sync.

Ground coil set — pulls ring to stop Sync coil set — pulls ring to input speed Output — planet carrier

Controls

Ratio command50 %

Input shaft speed2400 rpm

Output load35 %

Coil coupling strength60 %

Ring / sun tooth ratio Z19.0

input

0 rpm

ring — 2nd input

0 rpm

output

0 rpm

ratio

0 : 1

output torque

0 N·m

ground coil

0 kW

sync coil

0 kW

ratio spread

0 : 1

COMMAND 0 %

Ground coil holds

The ring is pinned to the housing. All reaction torque goes to ground, the carrier turns at its slowest, and torque multiplication is at maximum. This is launch and low-speed pulling.

ω_ring = 0 → ratio = 1 + Z

COMMAND 1 – 99 %

Both coils oppose

Each coil pulls the ring toward a different speed. The ring settles where their torques cancel, and that balance point is the ratio. Opposing them stiffens the set against load disturbance — the reason two coils beat one.

ω_ring = ω_in · G_sync / (G_sync + G_gnd)

COMMAND 100 %

Sync coil locks

The ring is drawn up to input speed. With two members turning together the whole set rotates as one body, giving direct drive with no relative motion and nothing to wear.

ω_ring = ω_in → ratio = 1 : 1

02 — Regenerative braking

The brake is the generator

Lift off and the output shaft becomes the driver. The ground coil set now takes reaction torque from a gear set being back-driven, and every newton-metre it holds appears as current at its terminals. Braking effort and charge current are the same quantity.

Kinetic energy Coil torque Recovered electrical

Braking event

Regen demand55 %

Vehicle mass1600 kg

Entry speed80 km/h

road speed

0 km/h

brake torque

0 N·m

decel

0 g

recovering

0 kW

energy recovered

0 Wh

of available

0 %

03 — Three-stage planetary drive

Overdrive step-up, controlled 15:1, reverse idler

The production gear train is three planetary sets in series, not one. Stage 1 steps the ring-gear drive up before it reaches MG-Ring, giving the machine the extra rpm it needs to push the set into overdrive. Stage 2 is the controlled set — up to 15:1 — where MG-Ring's reaction and MG-Lock's clamp set the ratio, same roles as before. Stage 3 sits right after Stage 2's output and does nothing in forward drive; it's engaged only when a mechanical reverse is actually needed, at a fixed 3:1. (Assumption — correct me if a connection or ratio is off.)

Stage 1 + MG-Ring — step-up, variable reaction MG-Lock — carrier hold / direct-drive lock MG-Boost — direct torque add Stage 3 — reverse idler (red = reverse engaged)

Drive state

Input speed1800 rpm

Stage 1 step-up ratio3.0 : 1

Stage 2 ring speed target55 %

Stage 2 teeth Z (max 15:1)8.0

MG-Boost power0 %

input

0 rpm

stage 2 ring

0 rpm

MG-ring (post step-up)

0 rpm

stage 2 carrier

0 rpm

final output

0 rpm

overall ratio

1.00 :1

output torque

0 N·m

STAGE 1 — OVERDRIVE FEED

Step-up ahead of MG-Ring

Stage 2's ring speed is stepped up before it reaches MG-Ring, so a smaller, higher-speed machine can supply the reaction and still have headroom to push the ring past input speed — that's what gives the set its overdrive range.

ω_MG-ring = step-up · ω_ring

STAGE 2 — CONTROLLED 15:1

MG-Ring and MG-Lock set the ratio

Same roles as before: MG-Ring's commanded ring speed sets a continuously variable ratio through the Willis relation; engaging MG-Lock clamps the carrier and drives the ring to input speed for a direct 1:1 lock-up. Z can run up to 14, giving a maximum 15:1 spread.

ω_car = (ω_sun + Z·ω_ring)/(1+Z)

STAGE 3 — REVERSE IDLER

3:1, engaged only for reverse

In forward drive Stage 3 is a straight pass-through and does nothing to the ratio. Selecting reverse holds a different member of Stage 3, flipping output direction at a fixed 3:1 — a purely mechanical reverse, independent of the electric machines.

reverse: ω_out = −ω_stage2-carrier / 3

Hill holdback — downhill grade

Two independent brakes reach the carrier here. Stage 1's step-up multiplies the torque MG-Ring can react back through the ring. Separately, engine compression braking on the sun/input shaft reaches the carrier with even more leverage — a full (1+Z) rather than MG-Ring's (1+Z)/Z — since engine braking never passes through the step-up stage. Uses MG-Ring's torque rating and the Stage 1 / Stage 2 sliders above.

Vehicle mass1600 kg

Downhill grade8 %

Engine braking torque120 N·m

MG-Ring → carrier

0 N·m

engine brake → carrier

0 N·m

hold force available

0 kN

grade pull force

0 kN

max holdable grade

0 %

status

—

Figures are produced by a first-order model for illustration. Ratio follows the Willis relation ω_carrier = (ω_sun + Z·ω_ring) / (1 + Z); ring speed settles where the two coil torques balance against gear-set reaction, ω_ring = (G_s·ω_in − T_react) / (G_s + G_g). Regen figures assume a recovery efficiency of 0.72 and ignore aerodynamic and rolling losses. CDR Controlled Magnetics Inc.

Global Branch