Datum chain
Trace shaft, bearing, endshield and resolver mounting surfaces.
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Vincent@vanguard-tech.cn
Motor Feedback Assembly
Control the mounting datums, air gap and electrical zero before a position-feedback error becomes a motor-system problem.
Engineering Overview
A frameless resolver places its rotor on the motor shaft and its stator in the housing or endshield. The motor bearings and mounting features establish their relative position. Poor concentricity, tilt or axial location can disturb the sensor air gap; incorrect angular indexing can make the feedback angle wrong even when the mechanics are sound. Neither condition should be hidden by controller calibration without first understanding the assembly.
Trace shaft, bearing, endshield and resolver mounting surfaces.
Control radial clearance around the complete rotation.
Relate feedback angle to the motor's defined reference.
Verify sine/cosine outputs and repeatability after assembly.
Image Gallery
The first two illustrations show resolver principles. The motor photographs show general rotor, stator and bearing-interface references; they are not photos of the resolver model specified for a project.
Tolerance Strategy
Start with the resolver supplier's outline drawing: nominal air gap, allowable eccentricity, axial position and any mounting orientation requirements. Add shaft runout, bearing play, endshield bore location, mounting fit and thermal expansion to the tolerance stack. A single nominal air-gap value does not guarantee clearance at the worst angular position or operating temperature.
For a high-accuracy assembly, inspect the interfaces against common datums before the resolver is fixed in place. Excessive press force or uneven clamping can distort a bare resolver. Mounting procedures should therefore specify insertion direction, support surfaces and torque sequence.
Inspection Plan
| Stage | Measurement or Check | Why It Matters | Record for Traceability |
|---|---|---|---|
| Motor shaft | Resolver seat diameter, runout and shoulder face | Controls rotor location relative to the bearing axis | Datum setup and measured values |
| Endshield | Stator bore position and face perpendicularity | Controls stator location and potential tilt | Bore, face and bearing-seat results |
| Assembly | Axial seating, retaining method and free rotation | Detects incomplete seating or physical interference | Fixture ID and assembly sign-off |
| Electrical zero | Reference angle to motor phase or rotor-flux datum | Connects sensor angle to commutation reference | Offset value and calibration method |
| Final test | Sine/cosine waveform, amplitude balance and angle error | Detects wiring, alignment and sensor-performance issues | Waveforms and pass/fail limits |
Assembly Route
Identify the shaft axis, bearing seat and endshield locating features.
Verify dimensions and runout before installing sensor parts.
Seat it without distortion and secure it by the approved method.
Control bore location, axial position and lead routing.
Use the project-specific motor reference and calibration procedure.
Rotate through a full turn and check waveforms, error and repeatability.
Failure Diagnosis
| Observed Symptom | Possible Contributor | First Investigation |
|---|---|---|
| Angle error varies once per revolution | Eccentric mounting, tilt or shaft runout | Check mechanical datums and full-turn error plot |
| Constant angle offset | Electrical zero set incorrectly | Recheck index marks and calibration reference |
| Low or uneven signals | Axial offset, wiring issue or incorrect excitation | Compare raw channels with supplier test conditions |
| Intermittent signal | Lead strain or connector fault | Inspect harness route and continuity under movement |
| Contact or rubbing | Insufficient clearance or assembly distortion | Stop testing; inspect air gap and seating before restart |
Engineering Support
A resolver problem can originate outside the sensor itself: a bearing seat, shaft shoulder, endshield bore or retention feature may shift the final alignment. Shared datums and measured stack-ups make it easier to distinguish a component issue from an assembly issue.
Ningbo Vanguard Technologies supports motor rotor and stator components, precision machining, assembly process review and prototype validation. We can help translate resolver mounting requirements into drawing callouts and practical incoming and final inspection steps.
FAQ
For motor design, assembly and quality teams.
Calibration may reduce some measured angle error, but it does not restore mechanical clearance or remove contact risk. Inspect geometry first.
No. They are different interfaces with different datums and acceptance limits, even though both depend on the shaft and housing assembly.
After mechanical installation and before final motor-drive validation, using the motor's released reference and the chosen resolver-to-digital chain.
Raw-channel review can reveal wiring, amplitude balance or excitation problems that an angle value alone may hide.
Keep critical datum measurements, assembly method, electrical offset, waveform or angle-error results and traceability to the resolver and motor build.
Share the motor and resolver drawings for a manufacturability and inspection review.
