Protocol Architecture Tool

CANopen Servo Drive Load Calculator

Evaluate a CANopen servo drive for AGV/AMR bus load, CiA 402 mode fit, wiring limits, and EtherCAT tradeoffs before supplier selection. Contact us for review.

Published July 18, 2026. Last updated July 18, 2026.

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CANopen Servo Drive & CANopen Drives Load Calculator

Evaluate whether a single CANopen servo drive or a multi-axis CANopen drives network can support your AGV/AMR architecture, or whether the architecture needs EtherCAT before procurement.

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Architecture Parameters

Number of CANopen Drives (1-32)

How many motor controllers share the same CAN bus segment? Leave blank to see the recoverable empty state.

Motion Control Profile

Cyclic synchronous modes require continuous setpoint updates every SYNC cycle. Profile modes calculate trajectories internally.

Target SYNC Cycle Time

CAN Bus Baud Rate

Selected screen: 100 m trunk, 5.5 m max stub, 27.5 m accumulated drive stubs.

Main Trunk Length (m)

Approximate backbone length from controller to last node.

Longest Drive Stub (m)

Longest drop from the bus trunk to a drive. Count controller and I/O drops separately before release.

Architecture Feasibility Result

Live screening complete.

Estimated Bus Load

25.5%

Requires approx. 127,600 bits/sec on a 500 kbps network.

Topology Screen

Trunk: 18 m / 100 m
Max stub: 0.4 m / 5.5 m
Drive drops: 0.8 m / 27.5 m

Screened against 500 kbit/s. Add controller and I/O drops before final harness release.

Selected trunk and drive-drop lengths stay inside the public lower-layer screen for 500 kbit/s.

Calculation Assumptions

CSP assumes one 8-byte RxPDO and one 8-byte TxPDO per drive on every SYNC cycle.
Profile mode assumes intermittent target updates, not continuous centralized trajectory streaming.
Overhead adds 10% for heartbeat, service, EMCY, and burst margin; supplier traces decide final acceptance.
The topology check covers drive drops only and does not certify EMC, termination, shielding, or safety behavior.

Architecture Valid

A bus load of 25.5% leaves bandwidth for arbitration, diagnostics, and sporadic errors, while the entered drive wiring stays inside the selected topology screen. CANopen remains a candidate if EDS files prove the needed CiA 402 modes and STO evidence.

Next Step

Use this architecture as a candidate baseline, then validate EDS mode support, wiring length, and STO evidence with the selected drive vendor.

CANopen Servo Drive and CANopen Drives Capability Report

Analysis of CANopen servo and stepper drives for mobile robotics and AGV powertrains. The plural keyword "CANopen drives" is treated as the same canonical decision task: choose and validate one or more CiA 402 CANopen servo drives on a shared network.

Key Architecture Conclusions

Profile Mode offloads the bus: For mobile robots (AGVs), using Profile Position (PP) or Profile Velocity (PV) modes allows the drive to handle the trajectory, reducing bus load significantly compared to centralized cyclic modes. Confirm the exact mode in each vendor EDS file.
The 40-60% review zone: In Cyclic Synchronous Position (CSP) mode, higher average bus load increases arbitration delay risk. Treat 40% as a review trigger and 60% as a practical architecture stop unless pilot logs prove otherwise.
Bit rate is also a wiring decision: Lowering the bit rate can improve trunk and stub margin, but it also reduces cyclic bandwidth. Screen bus load and topology together before approving a CANopen drive segment.
SYNC Frame Vulnerability: Even a high-priority SYNC frame can wait behind an already transmitting Classic CAN frame. The exact delay depends on payload, bit stuffing, bit rate, and topology, so final timing evidence must come from bus traces.
EtherCAT as the CSP upgrade path: For 4+ axes requiring strict synchronization at <2ms cycles, EtherCAT usually gives more timing margin than Classic CANopen. Use CANopen drives for simpler decentralized motion or slower synchronized loops.

CiA 402 Standardization

Industrial CANopen servo and stepper drives commonly use the CiA 402 device profile. This standardizes the state machine (Control/Status Words) and operation modes (Profile Position, Cyclic Synchronous Velocity, etc.). It improves integration consistency, but vendor swap still requires EDS, PDO, parameter, and firmware validation.

Deterministic Limits

Classic CAN relies on bit-wise arbitration. It is not a scheduled, distributed-clock network like EtherCAT. Keep cyclic traffic conservative and verify timing traces before freezing a multi-axis CANopen drive architecture.

Functional Safety (STO)

Standard CANopen communication is not safety-rated. An AGV using CANopen drives must use hardwired STO or certified safety communication evidence; normal CiA 402 control words are not an emergency-stop case.

Understanding SYNC Jitter in CANopen

In CANopen, the master broadcasts a SYNC object (default ID 0x80) to synchronize the control loops of all drives. Drives use this signal to apply new setpoints simultaneously.

However, Classic CAN is an asynchronous bus with non-destructive bit-wise arbitration. If a node, such as an IO module or another drive sending a TxPDO, starts transmitting right before the master tries to send the SYNC frame, the master must wait until the bus is idle.

Timing boundary: A high-priority SYNC frame can still wait behind a frame that is already on the wire. At 1 Mbit/s, a full Classic CAN data frame can occupy roughly a tenth-plus of a millisecond depending on payload and stuffing. Treat the calculator as a screening model and confirm the final number with bus traces.

Mitigation Strategies:

Use PDO frame offsets (transmission delays) to prevent multiple drives from attempting to answer SYNC simultaneously.
Keep the overall average bus load in the conservative range and review any result above 40%.
Avoid high volumes of low-priority traffic like SDOs during active motion.

Wiring and Bit-Rate Boundaries for CANopen Drives

Public CANopen lower-layer guidance gives practical screens for trunk length and stubs. These limits are not a replacement for final EMC validation, but they prevent an early architecture from depending on an impossible CANopen wiring envelope.

Bit rate	Bus length	Max stub	Accumulated stub	Decision implication
1 Mbit/s	25 m	1.5 m	7.5 m	Use only for compact machines with controlled wiring.
500 kbit/s	100 m	5.5 m	27.5 m	Common AMR/AGV planning point when cycle time can relax.
250 kbit/s	250 m	11 m	55 m	More wiring margin, less bandwidth for cyclic motion.
125 kbit/s	500 m	22 m	110 m	Fit for slow diagnostics/control, not tight CSP loops.

Calculator Limits and Source Traceability

When selecting a CANopen drive, engineers must evaluate whether the communication bus can handle the required control loops. While a central vehicle controller might calculate kinematics every millisecond, transmitting that over CAN to multiple drives may saturate the bus.

Addressing Bus Saturation

Profile Modes (PP/PV): Offload the trajectory calculation to the drive. The master sends a final target position, and the drive executes the acceleration/deceleration curve. This drastically reduces bus load.
Cyclic Modes (CSP/CSV): The master sends fine-grained setpoints every SYNC cycle. This requires high bandwidth and is the primary reason engineers enter the bus-load review zone.

Calculator Check	Planning Basis	Calculator Limit and Required Evidence
CSP traffic model	SYNC plus one RxPDO and one TxPDO per drive on every selected cycle.	Assumes Classic CAN 8-byte PDOs. Vendor PDO maps can add or remove frames.
Profile mode estimate	Profile Position / Velocity traffic is screened as one update every five cycles.	Use supplier traces when targets are streamed more often or diagnostics are active during motion.
Protocol overhead	Adds 10% for heartbeat, NMT, SDO service access, EMCY, and burst margin.	Treat 40% as a review trigger and 60% as an architecture stop until measured otherwise.
Topology gate	Checks selected bit rate against public trunk, per-stub, and accumulated-stub screens.	The tool checks drive drops only; add controller, I/O, and service-port drops before final harness release.

Evidence Parameter	Source & Date	Implementation Guidance
CiA 402 drive profile scope	CAN in Automation, CiA 402 series Accessed 2026-07-18	Supports the page boundary that CANopen servo drives, frequency inverters, and stepper drives share standardized behavior, operation modes, and state-machine concepts, but firmware-specific EDS files still decide exact mode support.
CANopen CC bit-rate and trunk-length envelope	CAN in Automation, CANopen lower layers Accessed 2026-07-18	Provides the public bit-rate planning table used for 1 Mbit/s, 500 kbit/s, 250 kbit/s, and 125 kbit/s wiring boundary notes.
Classic CAN payload and arbitration boundary	CAN in Automation, Designing a CAN network Accessed 2026-07-18	Grounds the tool model in Classic CAN limits: 1 Mbit/s maximum bit rate, 8-byte data field, and topology-dependent limits. The 40/60% thresholds are conservative engineering screens, not a CiA certification rule.
CANopen Safety and normal command separation	CAN in Automation, The CiA story Accessed 2026-07-18	Supports the safety boundary: normal CANopen drive communication is separate from CANopen Safety / EN 50325-5 or hardwired STO evidence.
EtherCAT as a synchronized-motion upgrade path	EtherCAT Technology Group, technology overview Accessed 2026-07-18	Supports EtherCAT as the distributed-clock/high-performance alternative. This page treats protocol timing numbers as planning signals; final cycle time and jitter must come from selected drive manuals and measured traces.

Modbus vs CANopen vs EtherCAT Drives

Many servo drives offer multiple protocols (often marketed as "wholesale Modbus/CANopen/EtherCAT servo drives"). It is critical to select the right one for the task:

Modbus (RTU/TCP): polling-oriented and best treated as monitoring or parameter access unless a vendor provides motion-specific timing evidence for the exact drive and controller.
CANopen: practical for small, cost-sensitive drive groups when CiA 402 modes, PDO maps, bus load, and topology stay inside measured limits. Tight 1-2 ms loops need trace evidence, not a generic protocol promise.
EtherCAT: the usual upgrade path when the machine needs tightly synchronized multi-axis motion or when CANopen fails the combined bandwidth/topology screen. Final timing still depends on the selected master, drives, and topology.

Read Protocol Comparison CAN bus Controller Fit Check Request Architecture Review

When CANopen Drives Fit and When They Do Not

Decision area	CANopen fit	Review trigger	Mitigation
Motion mode	Profile Position or Profile Velocity with drive-side trajectory generation.	Central controller sends cyclic setpoints to many axes at 1-2 ms.	Split segments, relax the cycle, or use EtherCAT for tight CSP groups.
Supplier evidence	EDS files, PDO maps, CiA 402 modes, heartbeat behavior, and fault logs are available before pilot build.	Marketing page says CANopen but omits EDS, supported modes, or PDO timing.	Hold purchase until the vendor provides EDS and sample bus traces under load.
Safety boundary	Normal CANopen controls motion and diagnostics; STO is handled by certified hardware or safety protocol evidence.	Emergency stop, STO, or SLS is described as a normal CANopen command only.	Use dual-channel STO wiring or documented CANopen Safety evidence; verify with the machine risk assessment.

Frequently Asked Questions

Is "CANopen drives" the same buying task as "CANopen servo drive"?

For this canonical page, yes. The plural phrase usually means selecting one or more CANopen servo or stepper drives for a shared machine architecture. The decision is still whether the selected CiA 402 CANopen drive hardware can support the required mode, cycle time, wiring, diagnostics, and safety boundary.

Why do suppliers offer "Modbus/CANopen/EtherCAT" multi-protocol drives?

Suppliers often use a shared power stage and motor control ASIC, leaving the communication interface to a plug-in module or firmware variant. This allows them to market a "wholesale Modbus/CANopen/EtherCAT servo drive" family. You still must order the exact protocol variant required for your controller architecture. Do not use Modbus for real-time motion.

Why use a 40-60% bus-load review zone?

The calculator uses 40% as a review trigger and 60% as a stop signal because arbitration delay rises as the bus gets busy. This is a conservative engineering screen, not a formal CiA pass/fail rule. Final acceptance needs traces with PDO, heartbeat, EMCY, and service traffic active.

Do all CANopen drives support CiA 402?

Many industrial CANopen servo and stepper drives implement CiA 402. However, support for specific modes like CSP or PP varies by firmware. Always check the Electronic Data Sheet (EDS).

What files should I request before approving a CANopen drive?

Ask for the EDS file, supported CiA 402 modes, default and configurable PDO maps, heartbeat behavior, EMCY object list, firmware version, wiring recommendations, and STO or safety documentation. Without those files, the bus-load result is only a concept screen.

Can I use CANopen drives for 4-wheel omnidirectional robots?

Yes, but 4 independently steered and driven wheels (8 axes) requiring 2ms CSP updates will likely saturate a 1 Mbit/s CANopen bus. EtherCAT is highly recommended for 8+ coordinated axes.

When should I stop evaluating CANopen and move to EtherCAT?

Stop if the calculator enters the critical range, the machine needs tight CSP/CSV/CST synchronization below 2 ms, or the supplier cannot provide repeatable bus traces under worst-case traffic. CANopen can still serve auxiliary axes, diagnostics, or slower decentralized motion in the same machine family.

Does lowering the CANopen bit rate always fix the design?

No. Lower bit rates usually give more trunk and stub margin, but they also reduce available cyclic bandwidth. Recalculate both bus load and topology after every bit-rate change.

Do I count controller and I/O module stubs?

Yes. The calculator estimates drive-drop total because the keyword task is drive selection. Before harness release, add every controller, I/O, service, and diagnostic drop to the accumulated stub review.

Can CANopen FD solve an overloaded drive network?

Only if the complete stack supports it: controller, drives, tools, EDS/firmware behavior, safety evidence, and service process. This page screens Classic CANopen because that is the common CiA 402 drive procurement path.

What bus trace should I capture in the pilot build?

Capture SYNC timing, RxPDO/TxPDO bursts, heartbeat intervals, EMCY events, SDO service traffic during motion, error counters, and measured bus load at the final bit rate and harness length.

How should I split a CANopen drive network?

Keep tightly coupled cyclic axes on the same reviewed segment, move auxiliary axes or I/O to a separate segment, and avoid mixing high-volume diagnostics with motion traffic during active control.

Validate the CANopen Drive Segment Before Supplier Freeze

Share the drive count, bit rate, control mode, harness envelope, EDS files, and pilot trace plan so the procurement review can separate acceptable CANopen architectures from designs that need EtherCAT or segmented CAN networks.

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