Yamaha developing power steering for motorcycles

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The barrage of rider aids on today’s bikes would be unthinkable to riders even a decade or so ago but Yamaha’s latest addition could be a game-changer – not only adding an extra layer of safety but opening the door to a rethink on steering geometry.

Yamaha’s electric power steering (EPS) will be used in anger for the first time on the works machines in this year’s All-Japan Motocross Championship, but there are plans to use the system on a variety of bikes. It’s a remarkably compact setup, but the fact it’s computer-controlled means that there’s huge potential to increase its range of abilities.

You might wonder why power steering is even worth considering. After all, in day-to-day riding a conventional setup doesn’t require bulging biceps. For motocross use, however, there’s more sense in that most straightforward element of the idea; anything that can reduce rider fatigue will be a benefit.

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But reducing the effort needed to turn the bars is just one element of the system. It also doubles as an active steering damper, counteracting external forces so you’re not left wrestling the bars to keep them pointing in your chosen direction. Again, motocross is a serious test of the idea, but it could be helpful on road bikes or other racers.

The power steering itself adopts magnetostrictive torque sensor technology from power-assisted bicycles to work out what you want it to do. On e-bicycles these torque sensors are used to tell when you’re pedalling, and how hard, sending that data to a control computer that interprets the amount of electric assistance needed. Here, it does the same, but on the bike’s steering.

The fact that EPS can tell the difference between the rider’s intentional inputs and the unwanted external influences means it can add stability without compromising responsiveness.

The possibilities that the system opens up are vast. The artificial stability it promises means that bikes could be designed with steeper steering head angles and less trail, making for sharper steering without incurring instability and tankslappers.

In much the same way that modern fighter aircraft are inherently unstable to the point where they can’t be flown without computer assistance, a future motorcycle could be made with steering geometry that couldn’t be imagined without EPS.

Similarly, increased trail, which would normally make for over-heavy steering, could be adopted, using the power assistance to make it feel light. Quite simply, the system could remove the shackles currently placed on designers by the compromise between stability and responsiveness.

The system is compact but it could be revolutionary

The system also means there’s potential to connect the steering with the IMU, traction control and cornering ABS, creating an holistic stability control system that modulates throttle, brakes and steering – all the main rider inputs – to help prevent accidents.

Yamaha’s MOTOBOT robot rider system has already shown that computers can ride a bike around a track, and the power steering system seen here is the last piece of the jigsaw when it comes to adapting the knowledge from that project into something that can be adopted on a real-world motorcycle.

Yamaha are not alone in developing systems like this. Honda’s Riding Assist concept bikes also use auto-steering setups, and BMW demonstrated a self-riding R1200GS in 2019.

Bosch, the biggest supplier of ABS, IMUs, traction control systems and radar setups for motorcycles, are also working on a similar tech, which could be offered to allcomers like their other safety systems.

Yamaha power steering explored

  • Feeling the force The magnetostrictive torque sensor monitors how much force you’re applying to the bars, sending that information to a control computer.
  • Computer control The computer interprets how much steering torque you’re trying to apply and sends the right amount of power to an actuator ahead of the steering head, turning the front wheel.
  • Staying on track If external forces try to move the front wheel – bumps, for instance – the system knows that command hasn’t come from bar inputs, so the actuator can resist the movement and work as a steering damper.
  • Clever but simple The entire setup is incredibly compact and doesn’t require a major redesign to the bike’s frame, forks or headstock. That means it should be easy to adopt. Yamaha say the plan is to “equip EPS on various motorcycles in order to provide a wide range of riders with greater motorcycling fun, safety, and comfort.”
  • Time to perfection As on cars with power steering, there’s still a physical connection between the bars and the front wheel so you don’t lose control if the system fails.
Ben Purvis

By Ben Purvis