AGV Motor Speed and RPM Selection Guide: 公式, 標準 & 工作範例
Selecting the right motor speed for an Automated Guided Vehicle (自動導引車) is not a single-parameter decision. It sits at the intersection of vehicle dynamics, gearbox design, battery constraints, and control-loop bandwidth. Get it wrong and you face either a sluggish robot that cannot meet throughput targets, or an over-speeding motor that overheats, wastes battery, and dies prematurely. This guide walks through the full engineering chain—from the fundamental speed-to-velocity formula through IEC 60034-1 duty cycle classification, NEMA MG1 design types, and manufacturer datasheet interpretation—to give you a repeatable workflow for matching motor RPM to any AGV platform.
Why Motor Speed Defines AGV Performance
Motor rated speed (轉速) directly governs three AGV performance pillars:
| Performance Pillar | How Motor Speed Affects It | 不匹配的結果 |
|---|---|---|
| Travel Velocity | Wheel speed = motor RPM ÷ gear ratio; vehicle speed = wheel RPM × wheel circumference | Motor too slow → AGV cannot meet cycle-time targets; motor too fast → excessive gear ratio needed, efficiency drops |
| 扭矩密度 | For a given power, higher-speed motors are smaller and lighter but produce less torque per amp | Undersized torque → stall on ramps, sluggish acceleration; oversized motor → wasted payload capacity and cost |
| 電池運轉時間 | BLDC motors peak in efficiency at 70–90% of rated RPM; operating far below this wastes energy as heat | Poor efficiency zone → 15–30% shorter battery life per charge cycle, more charging stops, lower fleet OEE |
Industry data from AGV fleet operators shows that motors consistently running below 50% of rated RPM—common in over-geared designs—experience 20–35% higher energy consumption and 40% shorter bearing life compared to motors operating in their optimal efficiency band [1].
快速解答: Motor RPM Ranges by AGV Payload Class
For engineering teams that need a fast reference before diving into calculations, the table below consolidates field-proven motor RPM ranges across six AGV payload categories. These values assume BLDC or BLDC servo motors paired with single-stage planetary gearboxes (efficiency ≥ 90%) and polyurethane wheels on epoxy floors.
| Payload Class | Typical AGV Type | Motor Rated RPM | 傳動比範圍 | Wheel RPM (output) | Vehicle Speed | 馬達功率 | 電壓 |
|---|---|---|---|---|---|---|---|
| ≤ 100 公斤 | AGC / Light AMR | 3,000–5,000 | 5:1–10:1 | 300–600 | 0.8–2.0 m/s | 50–100 W | 24V |
| 100–300 kg | Warehouse AMR | 3,000–4,000 | 10:1–15:1 | 200–400 | 0.8–1.5 m/s | 100–200 W | 24V / 48V |
| 300–600 kg | Under-Riding AGV | 2,500–3,500 | 8:1–15:1 | 150–350 | 0.5–1.5 m/s | 200–400 W | 48V |
| 600–1,200 kg | Towing / Pallet AGV | 2,500–4,000 | 6:1–15:1 | 100–300 | 0.5–1.5 m/s | 400–750 W | 48V |
| 1,200–3,000 kg | Forklift AGV | 2,000–3,000 | 12:1–25:1 | 80–200 | 0.3–1.0 m/s | 750–1,500 W | 48V / 72V |
| 3,000–20,000 kg | Heavy-Duty AGV | 1,500–2,500 | 15:1–30:1 | 50–120 | 0.2–0.5 m/s | 1.5–5 kW+ | 72V / 80V |
Source: Consolidated from AGV manufacturer specifications [2][3], gear motor supplier data [4], and GreenSky Power’s AGV motor application guide [5].
The Speed–Torque–Gear Ratio Triangle
Every AGV drive design lives within a three-variable trade space. You cannot optimize one without affecting the other two. Understanding this triangle prevents the most common error in motor speed selection: choosing a motor based on speed alone and discovering the torque is inadequate only during prototype testing.
多變的 1: 電機額定轉速 (n否)
The rated speed is the RPM at which the motor delivers its rated torque continuously without exceeding its thermal class limit. For BLDC motors used in AGVs, this typically falls between 1,500 和 5,000 轉速. The rated speed is not the no-load speed (n0)—the no-load speed is typically 10–20% higher than the rated speed under load [6].
多變的 2: Gearbox Reduction Ratio (我)
The ratio converts motor shaft speed to wheel shaft speed. A higher ratio reduces output speed but multiplies output torque (minus gearbox efficiency losses). For AGV applications, ratios typically range from 5:1 (light AMR) 到 50:1 (heavy-duty), 和 15:1–25:1 being the most common range for warehouse AMRs [5].
多變的 3: Output Torque at Wheel (時間wheel)
This is the torque that actually reaches the drive wheel after gearbox reduction: 時間wheel = T發動機 × i × η, where η is gearbox efficiency (0.90–0.95 for planetary, 0.60–0.70 for worm gear). The wheel torque must exceed the sum of rolling resistance, gradient resistance, and acceleration inertia torque with a safety margin of 1.3–1.5× [7].
| Design Choice | Speed Effect | Efficiency Effect | When to Choose | |
|---|---|---|---|---|
| High motor RPM + high ratio | Normal–High vehicle speed | High wheel torque (ratio multiplies motor torque) | Good if motor stays in 70–90% rated RPM band | Standard warehouse AGV/AMR (recommended) |
| Low motor RPM + low ratio | Lower vehicle speed | Moderate wheel torque | Risk: motor may operate below optimal efficiency zone | Precision positioning AGV, cleanroom robots |
| High motor RPM + low ratio | Very high vehicle speed | Low wheel torque | Risk: insufficient acceleration torque, wheel slip | Long-distance towing AGV on flat floors |
| Low motor RPM + high ratio | Very low vehicle speed | Very high wheel torque | Risk: motor overheating at low RPM, poor cooling | Heavy-duty AGV (5+ 噸) with multi-motor drive |
核心公式: Motor RPM to Vehicle Speed
The fundamental equation linking motor speed to AGV linear velocity is:
v = (2 × π × r × n發動機) ÷ (60 × i)
在哪裡:
- v = AGV travel speed (多發性硬化症)
- r = drive wheel radius (米)
- n發動機 = motor rotational speed (轉速)
- 我 = gearbox reduction ratio (dimensionless)
Reverse Calculation: Deriving Gear Ratio from Target Speed
In practice, engineers usually know the desired vehicle speed and wheel diameter, then solve for the required gear ratio given a motor’s rated RPM:
i = (2 × π × r × n發動機) ÷ (60 × v)
For quick estimates, the wheel RPM can be calculated independently:
nwheel = (v × 60) ÷ (π × D) where D = wheel diameter (米)
然後: i = n發動機 ÷ nwheel
Numerical Example
Target: 1.2 m/s travel speed, 200 mm wheel diameter (r = 0.1 米), motor rated at 3,000 轉速.
- Wheel RPM = (1.2 × 60) ÷ (π × 0.2) = 72 ÷ 0.628 ≈ 114.6 轉速
- Gear ratio = 3,000 ÷ 114.6 ≈ 26.2
- Select standard ratio 25:1 或者 30:1 (nearest available)
- Verify actual speed at 25:1: v = (2π × 0.1 × 3000) ÷ (60 × 25) = 1.256 m/s ✓
- Verify actual speed at 30:1: v = (2π × 0.1 × 3000) ÷ (60 × 30) = 1.047 多發性硬化症 (slightly below target)
This example illustrates why motor speed selection and gear ratio selection must be performed iteratively—you rarely get an exact match with standard ratios [3][7].
Reading the Speed-Torque Curve: Maxon and Faulhaber Methodology
Motor datasheets from leading manufacturers like 麥克森 和 Faulhaber present speed-torque characteristics as a linear graph. Understanding how to read this graph is essential for verifying that your selected motor speed will deliver the required torque under actual AGV load conditions.
The Speed-Torque Line (Maxon Methodology)
Maxon’s motor selection methodology defines the speed-torque relationship as a straight line from no-load speed (n0) at zero torque to stall torque (米H) at zero speed [6]:
n = n0 - (Δn/ΔM) × M
在哪裡:
- n0 = kn × UMot (no-load speed = speed constant × applied voltage)
- Δn/ΔM = speed-torque gradient (slope of the line, in RPM per mNm)
- 米 = instantaneous motor torque
Key insight from Maxon: the slope Δn/ΔM is a mechanical constant determined by the motor’s winding geometry and magnetic circuit—it does not change with voltage. Changing the applied voltage shifts the line up or down (parallel translation) but does not change the slope. This means a motor’s “powerfulness” (how much speed it retains under load) is fixed by design, not by the supply voltage [6].
Operating Range Rules (Faulhaber Methodology)
Faulhaber’s DC motor technical documentation recommends that for optimal motor life and efficiency, the operating point should satisfy [8]:
- Required speed n ≥ n0 / 2 (operate above half the no-load speed)
- Required load torque M ≤ MH / 2 (operate below half the stall torque)
- For continuous duty: stay within the continuous operation zone defined by the thermal limit curve
For AGV applications, this translates to a practical rule: select a motor whose rated speed is 1.5–2× the speed you actually need at the motor shaft, then use the gearbox ratio to reduce to the target wheel speed. This keeps the motor in its efficient upper-speed zone and leaves torque headroom for acceleration transients [6][8].
Maxon’s 20% Tolerance Rule
When selecting a motor winding for a specific AGV application, Maxon recommends adding a 20% margin to the calculated speed constant to account for tolerances in winding resistance, magnet strength, and load variability [6]:
kn ≥ 1.2 × (nmax,必需的 + (Δn/ΔM)avg × Mmax) ÷ UMot
This ensures that even with manufacturing tolerances (Maxon publishes ±10% on no-load speed and ±50% on no-load current), the motor will still meet the AGV’s speed requirement under worst-case conditions [9].
Gearbox Ratio Selection by AGV Type
Different AGV architectures demand different speed-torque trade-offs. The table below maps six common AGV types to their recommended motor RPM, 齒輪比, and output characteristics, based on consolidated data from AGV motor manufacturers and system integrators [2][3][5].
| AGV Type | Motor RPM | 齒輪比 | Output Characteristic | Recommended Gearbox | Key Design Constraint |
|---|---|---|---|---|---|
| Under-Riding AGV | 2,500–3,500 | 8:1–12:1 | Low speed, 高扭矩, 精準定位 | 行星 (low backlash ≤ 5 arc-min) | Top-lift torque must exceed full-load gravity torque |
| Forklift AGV | 2,000–3,000 | 12:1–20:1 | Ultra-high starting torque, strong braking | 行星 (2-階段) or worm gear (self-locking) | Torque priority over speed; electromagnetic brake required |
| Towing AGV | 2,500–4,000 | 6:1–10:1 | Medium speed, long continuous run | 行星 (螺旋狀的, 高效率) | Thermal management for extended duty cycles |
| Load-Carrying AGV | 3,000–4,000 | 5:1–8:1 | 快速回應, agile steering | Compact planetary or integrated drive wheel | Balance speed and acceleration performance |
| Differential Drive AGV | 3,000–4,500 | 5:1–8:1 | 快速回應, sensitive steering control | Low-backlash planetary (≤ 3 arc-min) | Left/right wheel torque matching for straight-line tracking |
| Heavy-Duty AGV (5–20t) | 1,500–2,500 | 15:1–25:1 | Extreme torque, low-speed stability | Multi-stage planetary (2–3 stage) | Multi-motor synchronized drive; redundant cooling |
Gearbox Efficiency Impact on Effective Speed
The gearbox efficiency directly reduces the output torque (and thus the effective tractive force), but it does not change the output speed. 然而, because the motor must produce more torque to compensate for gearbox losses, the motor’s actual operating speed drops along the speed-torque line. This means a worm gearbox (小時= 0.65) causes the motor to run 10–15% slower than a planetary gearbox (小時= 0.92) at the same load, because the motor must deliver more torque to achieve the same wheel output [7].
| Gearbox Type | 效率 | Max Single-Stage Ratio | 反彈 | 噪音水平 | AGV Suitability |
|---|---|---|---|---|---|
| 行星 | 90–95% | 3:1–10:1 (最多 100:1 multi-stage) | 3–15 arc-min | 低的 | Standard for all AGV types |
| Worm Gear | 60–75% | 5:1–60:1 | 15–30 arc-min | 低的 | Forklift AGV (self-locking benefit) |
| Parallel Shaft | 90–94% | 3:1–30:1 | 15–30 arc-min | 緩和 | Light-load AGV, cost-sensitive |
| Harmonic Drive | 85–90% | 50:1–200:1 | ≤ 1 arc-min | 非常低 | 精準定位, 機器人關節 |
國際電工委員會 60034-1: Duty Cycle Classifications for AGV Speed Selection
Motor speed selection cannot be separated from thermal considerations. 國際電工委員會 60034-1:2022 (版 15) defines ten duty cycle classifications (S1–S10) that determine how long a motor can sustain its rated speed and torque without exceeding thermal limits. For AGV applications, three classifications are most relevant [10][11].
S1 — Continuous Duty
The motor runs at constant rated load long enough to reach thermal steady state. This applies to towing AGVs on long-distance transport loops. The rated speed and torque on the motor nameplate are S1 values—selecting a motor based on nameplate ratings is safe only if your AGV operates in S1 mode.
S3 — Intermittent Periodic Duty
The motor cycles between run and stop periods without significant thermal equilibrium. This is the most common AGV duty cycle: pick-up → travel → drop-off → idle → repeat. S3 is expressed as a percentage (例如, S3-40% means the motor is energized 40% of the cycle time). A motor rated for S3-40% can deliver 1.6× its S1 torque during the on-period, but only if the off-period provides sufficient cooling.
S4 — Intermittent Periodic Duty with Starting
Similar to S3 but includes a significant starting (加速度) phase that contributes to heating. This applies to AGVs with frequent start-stop cycles (例如, warehouse AMRs navigating through aisles with obstacle avoidance).
| 國際電工委員會 60034-1 班級 | AGV Application | Thermal Impact on Speed | Derating Factor vs. S1 | Insulation Class Recommendation |
|---|---|---|---|---|
| S1 (連續的) | Towing AGV, long-distance transport | Full thermal load; rated speed = max continuous speed | 1.0 (baseline) | F級 (155℃) minimum |
| S3-40% (Intermittent) | Warehouse AMR, pallet mover | Motor can run at higher torque between rests; speed maintained during on-period | 1.6× torque during on-period | F級 (155℃) or Class B (130℃) |
| S4 (Intermittent + Starting) | High-frequency pick-and-place AGV | Starting current adds thermal load; effective continuous speed reduced | 1.3–1.5× torque, shorter duty | F級 (155℃) recommended |
| S2 (Short-Time) | AGV steering motor (intermittent rotation) | Rated for short burst; must cool before next cycle | 2.0× torque for ≤ 30 分鐘 | B級 (130℃) acceptable |
For AGV motor selection, the practical implication is: if your AGV operates in S3 or S4 mode, you can select a motor with a lower S1-rated speed than a pure S1 calculation would suggest, because the intermittent duty allows the motor to run harder during active periods. 然而, you must verify that the RMS (root-mean-square) torque over the full cycle does not exceed the motor’s S1 rated torque [11].
NEMA MG 1: Standard Speed Ratings and Design Types
While AGV motors are typically DC-powered (BLDC 或有刷), many AGV systems in North American facilities also integrate AC induction motors for auxiliary functions (泵, lifts, 輸送機). NEMA MG 1-2021 defines standard speed ratings that engineers should recognize when specifying complete AGV systems [12].
NEMA Standard Speeds at 60 赫茲
The synchronous speed of an AC motor is determined by the formula: 否s = 120 × f ÷ P, where f = frequency (赫茲) and P = number of poles.
| 波蘭人 | 同步速度 (60 赫茲) | Typical Full-Load Speed | AGV Application |
|---|---|---|---|
| 2 | 3,600 轉速 | 3,450–3,540 RPM | High-speed auxiliary pump (rare in AGV) |
| 4 | 1,800 轉速 | 1,725–1,780 RPM | Hydraulic lift pump motor |
| 6 | 1,200 轉速 | 1,140–1,175 RPM | Conveyor drive (on-board AGV belt) |
| 8 | 900 轉速 | 850–870 RPM | Low-speed high-torque auxiliary |
NEMA Design Types and IEC Equivalents
NEMA MG 1 classifies motor designs by their torque-speed characteristics. For AGV auxiliary AC motors, the design type determines starting behavior under load [12][13].
| NEMA Design | IEC Equivalent | 啟動扭力 | Breakdown Torque | Slip at Full Load | AGV Suitability |
|---|---|---|---|---|---|
| Design A | — | Normal | 高的 (>200%) | < 5% | 不推薦 (high starting current) |
| Design B | Design N | Normal (150–280%) | 200–250% | 3–5% | Standard AGV auxiliary motors (most common) |
| Design C | Design H | 高的 (200–250%) | 190–225% | 3–5% | AGV hydraulic lift (高啟動扭力) |
| Design D | — | 非常高 (275%+) | — | 5–13% | AGV traction (high slip, 高啟動扭力) |
For the primary AGV drive motor (無刷直流電機), NEMA MG 1 design types do not directly apply, but the thermal class and insulation rating standards are shared. Most AGV-grade BLDC motors use F級 (155℃) insulation per IEC 60034-1 / NEMA MG 1, with Class H (180℃) for high-ambient or heavy-duty applications [10][12].
Motor Speed Constants: kn, Kt, and Speed-Torque Gradient
Three constants define a motor’s speed behavior. Understanding them is essential for interpreting manufacturer datasheets and performing speed calculations that go beyond simple ratio division.
Speed Constant (kn)
Expressed in RPM per volt (RPM/V). Defines the no-load speed at a given voltage: n0 = kn × U. A higher kn means the motor spins faster at the same voltage but produces less torque per amp. For AGV BLDC motors, kn values typically range from 50–300 RPM/V (at 24V: 1,200–7,200 RPM no-load) [6].
扭矩常數 (Kt or k米)
Expressed in Nm/A (or mNm/A for small motors). Defines the torque produced per amp of current: M = Kt × I. Maxon notes that for their motors, torque and current are directly proportional, meaning the current axis on a speed-torque graph can be read as a parallel torque axis. Typical AGV BLDC motor Kt values range from 0.02–0.5 Nm/A [6].
Speed-Torque Gradient (Δn/ΔM)
Expressed in RPM per Nm (or RPM per mNm for small motors). Defines how much speed drops per unit of load torque increase: Δn/ΔM = n0 ÷ MH (no-load speed divided by stall torque). A flatter gradient (smaller value) means a more powerful motor that maintains speed under load. Maxon considers this the most meaningful single number for motor comparison, as it is a mechanical constant independent of winding choice [6].
| Motor Size (AGV Class) | Typical kn (RPM/V) | Typical Kt (Nm/A) | Typical Δn/ΔM (RPM/mNm) | No-Load Speed at 24V | Rated Speed at 24V |
|---|---|---|---|---|---|
| 57mm frame (≤100W) | 150–300 | 0.02–0.05 | 5–15 | 3,600–7,200 | 3,000–5,000 |
| 80mm frame (200–400W) | 80–150 | 0.05–0.15 | 3–8 | 1,920–3,600 | 2,500–3,500 |
| 100mm frame (500–750W) | 50–100 | 0.10–0.30 | 2–5 | 1,200–2,400 | 2,000–3,000 |
| 120mm+ frame (1kW+) | 30–60 | 0.20–0.50 | 1–3 | 720–1,440 | 1,500–2,500 |
筆記: Maxon publishes ±10% tolerance on no-load speed and ±50% tolerance on no-load current. Always include this tolerance in speed calculations, especially for AGV fleets where multiple motors must track the same speed [9].
Closed-Loop Speed Control: Encoder Resolution and PWM
Selecting the motor’s rated RPM is only half the equation—maintaining that speed precisely under varying load requires closed-loop control. AGV systems use encoder feedback to achieve speed regulation accuracy of ±0.5% to ±1.0% for standard industrial AGVs, and ±0.1% for high-precision positioning AGVs [3].
Encoder Resolution Impact on Speed Control
The encoder’s pulses per revolution (PPR) determines the minimum speed increment the controller can resolve:
Speed resolution = 60 ÷ (PPR × Tsample) (轉速)
Where Tsample is the control loop sampling period in seconds. 在 5 ms loop time (200 Hz update rate, typical for AGV motor controllers):
| Encoder PPR | Speed Resolution at 5ms Loop | Min Detectable Speed Change | Typical AGV Application |
|---|---|---|---|
| 1,000 PPR | 12 轉速 | ±0.4% at 3,000 轉速 | Low-cost AMR, AGC |
| 2,500 PPR | 4.8 轉速 | ±0.16% at 3,000 轉速 | Standard warehouse AGV |
| 5,000 PPR | 2.4 轉速 | ±0.08% at 3,000 轉速 | Precision positioning AGV |
| 17-bit absolute (131,072) | 0.09 轉速 | ±0.003% at 3,000 轉速 | Forklift AGV, high-precision docking |
PWM Frequency and Speed Ripple
The servo drive’s PWM switching frequency affects speed smoothness at the motor shaft. Typical AGV BLDC controllers use 16–20 kHz PWM, which is above the audible threshold and provides smooth current regulation. At lower PWM frequencies (8–10 kHz), speed ripple increases, causing visible wheel jitter at low speeds—an issue for AGVs performing precision docking [3].
Yaskawa Servo Speed Control Architecture
Yaskawa’s Sigma-5 and Sigma-X servo systems, widely used in industrial automation, illustrate best-in-class speed control architecture for AGV-class applications. The Sigma-5 series supports maximum speeds of 6,000 轉速 (low-inertia) 和 3,000 轉速 (medium-inertia) with 20-bit (1,044,576 counts/rev) encoder resolution. The speed control loop typically operates at 62.5 μs (16 千赫), enabling ±0.01% speed regulation—well beyond AGV requirements but illustrative of what closed-loop servo architecture achieves [14][15].
| 範圍 | Standard BLDC Controller | BLDC Servo (mid-range) | Yaskawa Sigma-5/X |
|---|---|---|---|
| Speed loop bandwidth | 200–500 Hz | 500–1,000 Hz | 1,000–2,500 Hz |
| Encoder resolution | 1,000–2,500 PPR | 2,500–5,000 PPR | 20-bit / 26-bit absolute |
| 調速 | ±0.5–1.0% | ±0.1–0.5% | ±0.01% |
| Max motor speed | 3,000–5,000 RPM | 3,000–6,000 RPM | 3,000–7,000 RPM |
| 峰值扭矩 | 150–200% rated | 200–300% rated | 300–350% rated |
Voltage Platform and Its Impact on Speed Range
AGV battery voltage directly constrains the motor’s achievable speed through the speed constant relationship (n0 = kn × U). Lower-voltage systems limit the maximum no-load speed, which in turn limits the available speed headroom for gear ratio optimization.
| Battery Voltage | Typical AGV Payload | Max Practical Motor RPM | Current at Rated Power | Wire/Connector Loss Impact | Recommended Motor Type |
|---|---|---|---|---|---|
| 24V | ≤ 300 公斤 | 3,000–5,000 | 高的 (8–20A per 100W) | Significant at >15A; use short runs | 無刷直流電機 (small frame) |
| 48V | 300–1,500 kg | 2,500–4,000 | 緩和 (4–10A per 100W) | Manageable; standard in warehouse AGV | BLDC servo (mainstream) |
| 72V | 1,500–3,000 kg | 2,000–3,500 | 降低 (3–7A per 100W) | 最小; allows longer cable runs | BLDC servo (high-power) |
| 80V+ | 3,000+ 公斤 | 1,500–3,000 | 低的 (2–5A per 100W) | 最小; heavy-duty cabling | BLDC servo / AC servo (with inverter) |
A critical design note: never operate a motor significantly below its rated voltage. A 48V-rated motor running on a 24V bus will only reach half its rated no-load speed, pushing the operating point into the low-efficiency zone and potentially causing thermal issues due to high current draw [3].
Worked Example 1: 500 kg Warehouse AMR
Design Requirements
- Total mass (vehicle + payload): 500 公斤
- Target travel speed: 1.5 多發性硬化症
- Wheel diameter: 200 毫米 (r = 0.1 米)
- Maximum gradient: 3% (1.7°)
- Acceleration target: 0.5 m/s²
- 電池: 48直流電壓
- 工作週期: S3-40% (warehouse pick-and-place)
Step-by-Step Speed Selection
| 步 | Action | Calculation | 結果 |
|---|---|---|---|
| 1 | Calculate required wheel RPM | nwheel = (1.5 × 60) ÷ (π × 0.2) | 143.2 轉速 |
| 2 | Select motor rated RPM (1.5–2× headroom) | Target motor RPM = 143.2 × 20 (initial ratio guess) | ~2,864 RPM → select 3,000 RPM motor |
| 3 | Calculate gear ratio | i = 3,000 ÷ 143.2 | 20.9 → select standard 20:1 |
| 4 | Verify actual speed at 20:1 | v = (2π × 0.1 × 3000) ÷ (60 × 20) | 1.57 m/s ✓ (exceeds 1.5 target) |
| 5 | Calculate rolling resistance force | Ff = 0.015 × 500 × 9.81 | 73.6 否 |
| 6 | Calculate gradient resistance force | F我 = 0.03 × 500 × 9.81 | 147.2 否 |
| 7 | Calculate acceleration resistance force | FA = 500 × 0.5 | 250 否 |
| 8 | Calculate total resistance (頂峰) | Ftotal = 73.6 + 147.2 + 250 | 470.8 否 |
| 9 | Calculate required wheel torque | 時間wheel = 470.8 × 0.1 | 47.1 牛米 |
| 10 | Calculate required motor torque (在 20:1, η=0.92) | 時間發動機 = 47.1 ÷ (20 × 0.92) | 2.56 牛米 |
| 11 | Apply safety factor (1.3×) | 時間發動機,rated = 2.56 × 1.3 | 3.33 牛米 |
| 12 | Select motor: 48V, 3,000 轉速, ≥3.3 Nm rated torque | Check datasheet speed-torque curve at 3,000 轉速 | Confirm rated torque ≥ 3.3 Nm at 3,000 轉速 |
| 13 | Verify RMS torque for S3-40% duty | 時間rms = √[(時間頂峰² × 0.4 + 時間idle² × 0.6)] | Verify Trms ≤ motor S1 rated torque |
結果: Select a 48V BLDC servo motor rated at 3,000 RPM with ≥ 3.3 Nm continuous rated torque, paired with a 20:1 single-stage planetary gearbox (η ≥ 92%, backlash ≤ 10 arc-min). This configuration delivers 1.57 m/s top speed with adequate torque margin for 3% gradients and 0.5 m/s² acceleration under 500 kg total mass [5][7].
Worked Example 2: 2,000 kg Forklift AGV
Design Requirements
- Total mass: 2,000 公斤
- Target travel speed: 0.8 多發性硬化症
- Wheel diameter: 300 毫米 (r = 0.15 米)
- Maximum gradient: 5% (2.9°)
- Acceleration target: 0.3 m/s²
- 電池: 72直流電壓
- 工作週期: S4 (frequent start-stop with lifting)
Step-by-Step Speed Selection
| 步 | Action | Calculation | 結果 |
|---|---|---|---|
| 1 | Calculate required wheel RPM | nwheel = (0.8 × 60) ÷ (π × 0.3) | 50.9 轉速 |
| 2 | Select motor rated RPM (heavy-duty, lower speed) | Target: 2,500 轉速 (per payload class table) | 2,500 轉速 |
| 3 | Calculate gear ratio | i = 2,500 ÷ 50.9 | 49.1 → select 50:1 (2-stage planetary) |
| 4 | Verify actual speed at 50:1 | v = (2π × 0.15 × 2500) ÷ (60 × 50) | 0.785 多發性硬化症 (slightly below 0.8; acceptable with 2% margin) |
| 5 | Calculate rolling resistance force | Ff = 0.015 × 2000 × 9.81 | 294.3 否 |
| 6 | Calculate gradient resistance force (5%) | F我 = 0.05 × 2000 × 9.81 | 981.0 否 |
| 7 | Calculate acceleration resistance force | FA = 2000 × 0.3 | 600 否 |
| 8 | Calculate total resistance (頂峰) | Ftotal = 294.3 + 981.0 + 600 | 1,875.3 否 |
| 9 | Calculate required wheel torque (dual drive) | 時間wheel,per = (1875.3 ÷ 2) × 0.15 | 140.6 Nm per wheel |
| 10 | Calculate required motor torque (50:1, η=0.88 for 2-stage) | 時間發動機 = 140.6 ÷ (50 × 0.88) | 3.20 牛米 |
| 11 | Apply safety factor (1.5× for S4 duty) | 時間發動機,rated = 3.20 × 1.5 | 4.80 牛米 |
| 12 | Select motor: 72V, 2,500 轉速, ≥4.8 Nm rated torque | Check datasheet; verify thermal class F or H | Confirm; add temperature sensor for S4 monitoring |
結果: Dual 72V BLDC servo motors, 2,500 轉速, ≥ 4.8 Nm rated torque each, 和 50:1 2-階段行星齒輪箱 (η ≥ 88%), delivering 0.79 m/s top speed and 1,875 N peak tractive force for 2,000 kg forklift AGV on 5% gradients. The S4 duty cycle requires Class F insulation and integrated thermal sensors [7][10].
Common Speed Selection Mistakes
| # | Mistake | What Happens | How to Avoid |
|---|---|---|---|
| 1 | Using no-load speed instead of rated speed for ratio calculation | DC motor no-load speed is 10–20% higher than loaded speed; using it produces a ratio that delivers 10–20% less output speed than intended | Always use the speed at rated torque (from the speed-torque curve) for ratio calculations [4] |
| 2 | Selecting ratio based on speed only, ignoring torque verification | Ratio delivers correct speed but output torque is insufficient; motor stalls on ramps or during acceleration | Complete both speed calculation and torque verification before finalizing [4] |
| 3 | Choosing excessively high ratio “for extra torque” | Motor operates at very low speed, outside efficient zone; 過熱, poor cooling, wasted speed range | Match ratio to required speed with appropriate torque margin (1.3–1.5×), not maximum ratio [4] |
| 4 | Ignoring gearbox efficiency in motor speed calculation | Motor must produce more torque than calculated, pushing operating point down the speed-torque line; actual speed 5–15% lower than expected | Include gearbox η in torque calculation; verify resulting motor speed on speed-torque curve [7] |
| 5 | Selecting motor voltage below battery bus voltage | Motor reaches only fraction of rated speed; high current draw, thermal issues, 效率降低 | Match motor rated voltage to battery nominal voltage; never undervolt significantly [3] |
| 6 | Not verifying RMS torque for intermittent duty | Motor passes peak torque check but fails thermal check over full cycle; overheating during multi-shift operation | Calculate RMS torque over full duty cycle; verify ≤ S1 rated torque per IEC 60034-1 [11] |
| 7 | Ignoring motor speed tolerances (Maxon ±10% on n0) | Fleet motors run at different speeds; straight-line tracking fails, differential AGV veers off course | Apply 20% margin per Maxon methodology; use closed-loop speed synchronization [6][9] |
7-Step Motor Speed Selection Workflow
Based on the engineering principles, 標準, and manufacturer methodologies covered above, the following workflow provides a repeatable process for AGV motor speed selection:
| 步 | Action | Input | 輸出 | 標準 / Reference |
|---|---|---|---|---|
| 1 | Define vehicle parameters | Total mass, target speed, max gradient, 加速度, wheel diameter, 電池電壓 | Design requirement sheet | — |
| 2 | Calculate required wheel RPM | nwheel = (v × 60) ÷ (π × D) | Wheel RPM at target speed | Basic kinematics |
| 3 | Select motor rated RPM from payload class table | Payload class → motor RPM range (see Quick Answer table) | Candidate motor RPM | [2][5] |
| 4 | Calculate gear ratio and verify speed | i = n發動機 ÷ nwheel; verify v = (2π × r × n發動機) ÷ (60 × i) | Candidate ratio; verified speed | [3][7] |
| 5 | Verify torque on speed-torque curve | Calculate T發動機 = Twheel ÷ (i × η); apply 1.3–1.5× safety; check on datasheet curve at rated RPM | Confirmed motor torque rating | Maxon methodology [6]; Faulhaber rules [8] |
| 6 | Verify thermal duty cycle | Determine IEC 60034-1 duty class (S1/S3/S4); calculate RMS torque; verify ≤ S1 rated torque | Thermal pass/fail; insulation class | 國際電工委員會 60034-1:2022 [10][11] |
| 7 | Apply tolerance margin and finalize | Add 20% speed margin (Maxon rule); select standard ratio; specify encoder PPR and IP rating | Final motor + gearbox specification | Maxon tolerance [9]; NEMA MG 1 [12] |
Academic Research on AGV Motor Speed Optimization
Several peer-reviewed IEEE papers have addressed motor speed optimization for AGV and mobile robot platforms:
- Energy-optimal speed profiles — Jaramillo-Morales et al. (2020) demonstrated that optimized speed profiles for differential-drive mobile robots can achieve significant energy savings compared to trapezoidal profiles, by operating motors closer to their peak efficiency RPM during acceleration phases [16].
- BLDC motor speed control for self-driving robots — Bae et al. (2020) presented sensorless speed estimation for in-wheel BLDC motors, showing improved low-speed control performance by compensating for Hall sensor lag—a relevant finding for AGVs operating at low wheel RPM [17].
- Dual-PM motor design for AGV — Lin et al. (2020) proposed a novel direct-drive dual-PM motor specifically designed for electric AGVs, achieving high efficiency across a wide speed range by reducing torque ripple through split-tooth stator design [18].
- Fuzzy speed control — Kodagoda et al. (2002, cited 250+ 次) developed fuzzy PD-PI controllers for AGV speed and steering, demonstrating that intelligent control can decouple speed from steering and maintain stable speed under varying load—a foundational result for AGV speed regulation [19].
- Intelligent speed controllers comparison — Khan et al. (2025) compared PID, FLC, ANFIS, and MPC controllers for DC motor speed regulation in wheeled autonomous robots, providing quantitative guidance on controller selection for different speed-regulation requirements [20].
These studies collectively reinforce the principle that motor speed selection is not just a mechanical ratio calculation but must be coupled with control architecture design to achieve the speed regulation precision that AGV navigation systems demand.
常問問題: AGV Motor Speed and RPM Selection
What is the typical RPM range for AGV motors?
AGV motors typically operate in the 1,500–5,000 RPM rated speed range, with 2,500–3,500 RPM being the most common for warehouse AMRs and logistics AGVs (500–1,200 kg payload). Light AMRs (≤100 kg) may use motors up to 5,000 轉速, while heavy-duty AGVs (3,000+ 公斤) typically use 1,500–2,500 RPM motors with high gear ratios (15:1–30:1) [2][5].
How do I calculate the gear ratio from motor RPM to wheel speed?
The formula is: 齒輪比 (我) = motor RPM ÷ wheel RPM. Wheel RPM = (target speed in m/s × 60) ÷ (π × wheel diameter in meters). 例如, A 3,000 RPM motor with a 200 mm wheel at 1.5 m/s target speed: wheel RPM = (1.5 × 60) ÷ (π × 0.2) = 143 轉速; ratio = 3,000 ÷ 143 ≈ 21:1 [3][7].
Should I use no-load speed or rated speed for gear ratio calculation?
Always use the 額定速度 (speed at rated torque), not the no-load speed. DC and BLDC motors run 10–20% slower under load than at no load. Using no-load speed will produce a ratio that delivers 10–20% less output speed than intended under actual AGV load conditions [4][6].
What happens if my motor runs too slowly for the application?
If the motor operates far below its rated RPM (以下 50% of rated), it enters a low-efficiency zone where: (1) energy consumption increases 15–35%, (2) 冷卻風扇 (if shaft-mounted) provide insufficient airflow, (3) current draw increases to maintain torque, accelerating thermal aging, 和 (4) battery runtime decreases proportionally [1][6].
How does IEC 60034-1 duty cycle classification affect motor speed selection?
國際電工委員會 60034-1 defines duty cycles S1–S10. For AGVs operating in S3 (intermittent) or S4 (intermittent with starting) 模式, the motor can deliver 1.3–1.6× its S1-rated torque during active periods. This means you can select a motor with a lower S1-rated speed than a pure continuous-duty calculation would suggest—provided the RMS torque over the full cycle does not exceed the motor’s S1 rating [10][11].
Can I use a 48V motor on a 24V AGV battery?
不推薦. A 48V motor on 24V will only reach approximately half its rated no-load speed, pushing the operating point into the low-efficiency zone. The motor will draw higher current to produce the same torque, increasing thermal load and reducing bearing life. Always match the motor’s rated voltage to the battery bus voltage [3].
Need a Custom AGV Motor Solution?
Selecting the right motor speed for your AGV platform requires balancing kinematics, 熱管理, gearbox efficiency, 和控制架構. GreenSky Power manufactures 無刷直流電機, 行星齒輪箱, 和 custom electric motor solutions specifically optimized for AGV and AMR drive systems. Our engineering team can help you calculate the optimal motor RPM, 齒輪比, and voltage platform for your specific payload, 速度, and duty cycle requirements. 聯繫我們 for a technical consultation or request a product specification sheet for your AGV motor project.
For more AGV motor engineering resources, see our related guides:
- 如何為 AGV 應用選擇電機: 完整的選擇指南
- Motor for AGV: Complete Selection Guide — Types, Torque Calculation & 規格
- AGV馬達扭矩計算指南: 公式, 工作範例 & 馬達選型
- AGV需要多少扭矩? 具有工程標準的基於有效負載的答案
- AGV 與 AMR: Navigation, Flexibility, 安全, 成本 & 馬達選型
- AGV 的 BLDC 與伺服電機: 力矩, 精確, 成本——選擇哪一個?
- 正齒輪馬達與行星齒輪電機: 哪一款適合您的項目?
- 直驅馬達與齒輪馬達: 力矩, 效率, Precision — Which to Choose?
- 伺服馬達與步進電機: 力矩, 速度, 準確性 & Cost — How to Choose
- BLDC 馬達與伺服電機: Key Differences and Selection Guide
- Motor Controller Selection Guide for AGV and AMR Applications
- 馬達測試標準: 國際電工委員會, 沒有, and Best Practices
參考
- Jkong Motor. “AGV无刷电机的转速和减速比应该如何匹配?” Available at: http://jkongmotor.cn/agvwushuadianjidezhuansuhejiansubiyinggairuhepipei.html
- Jkong Motor. “直流无刷电机在自动引导车中的实际应用.” Available at: https://www.jkongmotor.cn/zhiliuwushuadianjizaizidongyindaochezhongdeshijiyingyong.html
- HKT Robot (AGVMotor.com). “Brushless Servo Motor for AGV: Key Specs and Selection Guide.” Available at: https://agvmotor.com/blogs/knowledge/brushless-servo-motor-for-agv
- SY Motor. “How to Select the Right Gear Reduction Ratio: A Practical Guide for Engineers and Procurement Teams.” Available at: https://www.symotor-hz.com/news/industry-news/how-to-select-the-right-gear-reduction-ratio-a-practical.html
- GreenSky Power. “如何為 AGV 應用選擇電機: Complete Selection Guide.” Available at: https://greensky-power.com/how-to-choose-a-motor-for-agv-applications/
- Maxon Precision Motors. “Motor Type Selection.” Published via A3 Association for Advancing Automation. Available at: https://www.automate.org/tech-papers/motor-type-selection
- Bicontrols (YK-Control). “AGV行走系统动力学计算与驱动选型指南:从整车阻力到舵轮、电机及驱动器匹配.” Available at: https://www.bicontrols.com/news_detail/73.html
- Faulhaber Drive Systems. “計算 & Formulas for Brush DC Motors” (White Paper). Available via Qmed at: https://qmed.com/when-selecting-a-brush-dc-motor-for-an-file104689.html
- 麥克森集團. “Motor Data and Simulation — Standard Tolerances.” Available at: https://support.maxongroup.com/hc/en-us/articles/360013761160-Motor-data-and-simulation
- 國際電工委員會. 國際電工委員會 60034-1:2022 — Rotating electrical machines — Part 1: Rating and performance (版 15). Geneva: 國際電工委員會.
- HYX Geological Equipment. “Low-Speed Motor Parameter Encyclopedia: Comprehensive Technical Guide for Industrial Selection.” Available at: http://www.hyxgeo.com/article/179424572649472.html
- 全國電氣製造商協會. NEMA MG 1-2021 — Motors and Generators. Rosslyn, VA: 沒有.
- The Engineering Toolbox. “Electric Motors — IEC and NEMA Standard Torques.” Available at: https://www.engineeringtoolbox.com/iec-nema-standards-torques-d_741.html
- Yaskawa Electric Corporation. “Sigma-5 Servo Family — Product Catalog.” Available at: https://www.yaskawa.com/delegate/getAttachment?documentId=BL.Sigma-5.01
- Yaskawa Electric Corporation. “Sigma-X Rotary Servomotors — Product Specifications.” Available at: https://yaskawa.co.uk/motion-control/sigma-x/sx-rotary-servomotors
- Jaramillo-Morales, M.F., Dogru, S., & Marques, l. (2020). “Generation of energy optimal speed profiles for a differential drive mobile robot with payload on straight trajectories.” 2020 IEEE International Symposium on Safety, 安全, and Rescue Robotics (SSRR), 136–141. DOI: 10.1109/SSRR50563.2020
- Bae, J., Lee, D.-H., & Cho, K. (2020). “Speed and Direction Control of Two In-wheel BLDC Motors for the Self-Driving Surveillance Robot.” 2020 IEEE International Conference on Mechatronics and Robotics Engineering (ICMRE). DOI: 10.1109/icmre49073.2020.9065011
- Lin, Q., Niu, S., Cai, F., Fu, W., & Shang, l. (2020). “Design and Optimization of a Novel Dual-PM Machine for Electric Vehicle Applications.” IEEE 車輛技術彙刊, 69(12), 14391–14400. DOI: 10.1109/TVT.2020.3034573
- Kodagoda, K.R.S., Wijesoma, W.S., & Teoh, E.K. (2002). “Fuzzy speed and steering control of an AGV.” IEEE Transactions on Control Systems Technology, 10(1), 112–120. DOI: 10.1109/87.974981
- Khan, H., Namazi, H., & Lenort, 右. (2025). “Advanced Intelligent Controllers Design and Simulation Analysis for Optimizing Speed Control of Autonomous Systems.” IEEEX. Available at: https://ieeexplore.ieee.org/document/11370730


