RBTXpert Debrief: The Vibration Problem Nobody Talks About in Robot Selection
Partner Resource: Epson Robots — GYROPLUS Technology: Taking Robot Performance to the Next Level
Content Type: Technical White Paper
Best For: Engineers and automation managers evaluating SCARA or 6-axis robots for high-speed, precision-critical applications
Why We Are Sharing This
Speed, payload, and precision are the three variables every robot spec sheet leads with. What most spec sheets do not explain is why improving one of them tends to degrade the others. The answer is vibration, and it is the hidden constraint that derails more robot selection decisions than any other single factor.
Epson’s GYROPLUS white paper addresses this problem at the engineering level. RBTX Learn is sharing it because it explains a concept that most buyers encounter only after a system is installed and underperforming. Understanding it before selection is significantly more useful.
The paper is a technology explainer rather than a product comparison, so it stops short of showing what the technology does to a spec sheet. We have added that piece below, along with the questions worth bringing to any vendor conversation on this subject.
What the Content Actually Covers
The Physics Problem Behind Every Speed-Precision Tradeoff
The paper opens with an honest explanation of why robot performance tradeoffs exist at all. Increasing speed and acceleration increases vibration in the robot arm. Higher vibration means longer settling time before the next process can execute. Much of the cycle time gained by running faster gets consumed waiting for the arm to stop moving, so the net improvement is often smaller than the speed increase suggested.
The root cause is a sensing problem. A robot controller estimates arm position and velocity from feedback at the motor encoder, which sits at the joint rather than at the tool point. Robot arms are not perfectly rigid, so they deflect. The paper is specific about what makes that deflection worse: distance from the motor to the end of the arm, higher speed, and heavier payload. It also names the factors that cause true angular velocity at the tip to diverge from the motor’s angular velocity, which is where this gets practical. Mechanical tolerances and friction contribute, and so do the attached load and peripherals such as end effectors and wiring.
That last point deserves emphasis, because it is the reason two teams running the same robot model report different behavior. The gripper, the cable pack, and the tooling you bolt on are part of the vibration problem, and none of them are in the spec sheet.
The control loop here is closed, but it is closed at the motor rather than at the tool point. That distinction between sensing where the actuator is and sensing where the work happens is the whole subject of the paper.
Why the Traditional Fix Creates New Problems
The common workaround for arm vibration is to make the arm stiffer. Stiffer arms deflect less and vibrate less. Stiffer arms are also heavier, and heavier arms require larger motors, larger gearboxes, and larger drive components. The robot grows in cost, energy consumption, and footprint. The vibration problem improves and the other problems get worse.
The paper maps this out in a tradeoff table that is worth reading in a particular way. The first two rows cover the speed side: increasing speed increases vibration and lengthens settling time, and compressing cycle time pushes settling time up as a share of it. The last three rows all describe the same mechanism, increasing arm rigidity, with three separate consequences: cost, energy consumption, and footprint. Read as one mechanism with three price tags rather than as three findings, it is a useful reference for any team that has been told to just use a bigger robot without being told what that actually costs.
Worth noting that arm stiffening is one approach among several. Command and input shaping, notch filtering, and learning-based control are software methods that address residual vibration without adding mass, and most modern controllers implement some version of them. The paper’s argument is that a sensor at the tool point addresses the problem at its source rather than compensating for it downstream, which is a reasonable position, though a buyer comparing vendors should know that vibration suppression is a crowded engineering space.
What GYROPLUS Actually Does Differently
Epson’s approach places a gyro sensor at the end of the robot arm instead of relying solely on motor encoder feedback. The sensor measures actual angular velocity at the tip and feeds that data continuously to the controller, which then issues motion commands based on measured arm behavior rather than an estimate derived from motor angle. Epson describes this as an industry first for continuous feedback from the end of the arm.
The engineering obstacle was size. Gyro sensors are used widely in applications such as vehicle navigation, but at roughly thumb-sized dimensions they were too large to integrate into a robot arm without adding meaningful mass. Epson’s answer draws on its quartz crystal manufacturing base and proprietary MEMS processing to produce a sensor at one one-hundredth the volume of conventional designs, small enough to balance on the end of a pencil lead. That is the number that makes the whole concept viable, because it is what allows integration without changing the robot’s weight, size, or inertia.
The sensor is built as a double-T crystal oscillator, a configuration Epson credits with a high signal-to-noise ratio, resistance to vibration and shock, and temperature stability. Those three properties matter more than they sound: a vibration sensor mounted on a vibrating arm in a factory needs to distinguish signal from its own environment. Combined with Epson’s control algorithms, the system is used to detect and damp both rotational and vertical vibration.
The stated result is that smaller, lighter arms can run faster moves, handle heavier payloads, and hold tighter positioning than traditional designs of equivalent size. The paper extends this to a substitution argument: applications that previously required Cartesian or gantry robots for speed and precision may now be servable by SCARA or 6-axis robots with a smaller footprint, less mass, simpler integration, and less complex programming.
In fairness, that is a claim about a class of applications rather than a rule. Gantries still win on long-stroke, large-envelope, and high-rigidity work, so treat the substitution question as one to test against your actual envelope and duty cycle rather than settle on a paper.
What the Spec Sheets Show
The white paper argues a mechanism without publishing a performance delta, which is normal for a technology explainer but leaves the practical question open. Epson’s product specifications answer part of it.
The closest like-for-like pair is the pre-GYROPLUS G3-251 and the GYROPLUS-equipped GX4 at 250 mm reach. Both are compact SCARAs at the same arm length.
| G3-251 | GX4-250 | |
|---|---|---|
| Repeatability J1 + J2 | +/- 0.008mm | +/- 0.008mm |
| Repeatability J3 | +/- 0.010 mm | +/- 0.010 mm |
| Repeatability J4 | +/- 0.005° | +/- 0.005° |
| Rated / max payload | 1 kg / 3 kg | 2 kg / 4 kg |
| Published cycle time | 0.36 s | 0.33 s |
Published static repeatability is identical across the two. The movement is in throughput at payload: a shorter published cycle time while rated payload doubles and maximum payload rises by a kilogram.
That is a useful result, and it is a more precise claim than “better accuracy.” GYROPLUS is a settling-time and throughput technology. If your application is limited by how precisely the arm can place a part when it is standing still, this is not the specification that will change your outcome. If it is limited by how long the arm rings after each move, or you are trying to raise payload without surrendering cycle time, that is exactly where the benefit lives.
However, these numbers come with two caveats. First, the GX4 is a generation removed from the G3 and GYROPLUS is one of several changes between them, including a higher-power-density arm design, so this is a generation-to-generation comparison rather than an isolated test of the sensor. Second, Epson’s cycle time figures are benchmark figures. The GX4 number is quoted for a round-trip arch motion of 300 mm horizontal and 25 mm vertical with a 2 kg payload on a tabletop model in boost mode, with path coordinates optimized for maximum speed. Confirm the test basis for any two robots before comparing their published cycle times, from any manufacturer.
Which Robots Have It
The paper does not identify the product line, which is worth knowing before the technology factors into a decision. GYROPLUS is the GX family.
- GX4 — 250, 300, and 350 mm reach, payloads to 4 kg
- GX8 — 450, 550, and 650 mm reach, payloads to 8 kg
- GX-B series — GX4B, GX8B, GX10B, and GX20B, with payloads from 4 to 20 kg and reach to one meter
- RS series — RS3, RS4, RS4C, and RS6C with reach up to 550 mm and payload up to 6 kg
The GX-B series is the more current development and the paper predates a full account of it. In that line, GYROPLUS is implemented in the intelligent servo drives of the RC700E controller rather than treated purely as an arm-level feature. That is a meaningful architectural shift for anyone reading the 2023 paper today, and it widens the payload range the technology covers considerably beyond what the paper’s compact-SCARA framing implies.
The RBTXpert Take
The practical value of this paper sits in the settling time explanation and the tradeoff mapping. Both belong in any serious robot evaluation. Three things to take from it:
Ask what share of quoted cycle time is settling time. When a vendor quotes a cycle time at a precision level, that number is a sum of moving time and settling time. A robot that moves fast and settles slowly may not outperform a robot that moves moderately and settles quickly, and the spec sheet will not tell you which one you are looking at. This applies to every manufacturer, not just this one.
Ask for position stabilization time, and specify the conditions. ISO 9283 already defines position stabilization time and position overshoot as testable characteristics alongside pose accuracy and repeatability, so the measurement is standardized even though vendors rarely publish it. That gives you a concrete request: ask for stabilization time measured under ISO 9283, at your payload, with your end effector and cable routing installed, on a move profile that resembles your application. Given that the paper itself names end effectors and wiring as sources of divergence between motor feedback and actual tip behavior, a stabilization figure measured on a bare arm tells you less than you need.
Know which constraint you are actually buying against. Repeatability and settling time are different specifications solving different problems. Vibration technologies of this kind address the second. Teams that shop for one while being limited by the other end up with a robot that meets its spec sheet and misses their throughput target.
Beyond the Epson-specific discussion, the paper gives buyers a framework for asking better questions across any SCARA or 6-axis evaluation. RBTX Learn recommends it for any team comparing robots where both speed and precision matter, which in practice describes most assembly, dispensing, and inspection work.
Access the full GYROPLUS technology paper Here.