[{"data":1,"prerenderedAt":504},["ShallowReactive",2],{"\u002Fen\u002Fblog\u002Fjoint-motor-selection-guide":3},{"id":4,"title":5,"alt":6,"author":7,"body":8,"date":492,"description":493,"extension":494,"image":495,"keywords":496,"locale":497,"meta":498,"navigation":499,"path":500,"seo":501,"stem":502,"updated":497,"__hash__":503},"blog\u002Fblog\u002Fen\u002Fjoint-motor-selection-guide.md","BXI 85\u002F70\u002F50 Joint Motor Selection Guide","BXI Robotics joint motor lineup","BXI Robotics",{"type":9,"value":10,"toc":480},"minimark",[11,15,19,24,268,279,283,286,328,332,353,357,385,389,409,413,427,431,434,438,444,450,456,462,468],[12,13,5],"h1",{"id":14},"bxi-857050-joint-motor-selection-guide",[16,17,18],"p",{},"BXI Robotics joint motors use a hollow-shaft planetary reduction design, with dual absolute encoders (magnetic input + inductive output) and cross-roller bearings across the lineup, plus MIT-protocol-compatible CAN\u002FCANFD communication. The actuators have been validated on multiple humanoid platforms under defined test conditions, and their modular design fits both robotic arms and legs in high-DOF embodied systems. This guide gives the full specs of the four main models, a breakdown of what each parameter means, and a practical workflow so engineering and procurement teams can select by torque and size.",[20,21,23],"h2",{"id":22},"full-spec-table","Full spec table",[25,26,27,49],"table",{},[28,29,30],"thead",{},[31,32,33,37,40,43,46],"tr",{},[34,35,36],"th",{},"Parameter",[34,38,39],{},"BXI8515-19",[34,41,42],{},"BXI7010-19",[34,44,45],{},"BXI5018-19",[34,47,48],{},"BXI5014-19",[50,51,52,70,87,101,115,129,145,159,176,192,209,225,240,254],"tbody",{},[31,53,54,58,61,64,67],{},[55,56,57],"td",{},"Rated torque",[55,59,60],{},"40 N·m",[55,62,63],{},"15 N·m",[55,65,66],{},"11 N·m",[55,68,69],{},"7 N·m",[31,71,72,75,78,81,84],{},[55,73,74],{},"Peak torque",[55,76,77],{},"150 N·m",[55,79,80],{},"50 N·m",[55,82,83],{},"35 N·m",[55,85,86],{},"25 N·m",[31,88,89,92,95,97,99],{},[55,90,91],{},"Rated voltage",[55,93,94],{},"24–48 V",[55,96,94],{},[55,98,94],{},[55,100,94],{},[31,102,103,106,109,111,113],{},[55,104,105],{},"No-load speed",[55,107,108],{},"200 rpm",[55,110,108],{},[55,112,108],{},[55,114,108],{},[31,116,117,120,123,125,127],{},[55,118,119],{},"Rated output speed",[55,121,122],{},"100 rpm",[55,124,122],{},[55,126,122],{},[55,128,122],{},[31,130,131,134,137,140,143],{},[55,132,133],{},"Peak phase current",[55,135,136],{},"90 A",[55,138,139],{},"60 A",[55,141,142],{},"30 A",[55,144,142],{},[31,146,147,150,153,155,157],{},[55,148,149],{},"Reduction ratio",[55,151,152],{},"19.5",[55,154,152],{},[55,156,152],{},[55,158,152],{},[31,160,161,164,167,170,173],{},[55,162,163],{},"Weight",[55,165,166],{},"1.4 kg",[55,168,169],{},"0.8 kg",[55,171,172],{},"0.55 kg",[55,174,175],{},"0.5 kg",[31,177,178,181,184,187,190],{},[55,179,180],{},"Installation diameter",[55,182,183],{},"99 mm",[55,185,186],{},"81 mm",[55,188,189],{},"64 mm",[55,191,189],{},[31,193,194,197,200,203,206],{},[55,195,196],{},"Height",[55,198,199],{},"73 mm",[55,201,202],{},"68 mm",[55,204,205],{},"70.5 mm",[55,207,208],{},"66.5 mm",[31,210,211,214,217,220,223],{},[55,212,213],{},"Hollow bore",[55,215,216],{},"10 mm",[55,218,219],{},"9 mm",[55,221,222],{},"6 mm",[55,224,222],{},[31,226,227,230,233,236,238],{},[55,228,229],{},"Encoder",[55,231,232],{},"Dual absolute (magnetic input + inductive output)",[55,234,235],{},"Same",[55,237,235],{},[55,239,235],{},[31,241,242,245,248,250,252],{},[55,243,244],{},"Bearing",[55,246,247],{},"Cross-roller bearing",[55,249,235],{},[55,251,235],{},[55,253,235],{},[31,255,256,259,262,264,266],{},[55,257,258],{},"Communication",[55,260,261],{},"CAN \u002F CANFD",[55,263,261],{},[55,265,261],{},[55,267,261],{},[269,270,271],"blockquote",{},[16,272,273,274,278],{},"Values are theoretical; actual values may vary by operating conditions. The first two digits denote the frame-size series (85\u002F70\u002F50), and the ",[275,276,277],"strong",{},"-19"," suffix corresponds to the ~19.5 reduction ratio.",[20,280,282],{"id":281},"how-to-read-the-key-parameters","How to read the key parameters",[16,284,285],{},"Understanding a few parameters up front avoids trial-and-error over \"is the torque enough\":",[287,288,289,304,310,316,322],"ul",{},[290,291,292,295,296,299,300,303],"li",{},[275,293,294],{},"Rated vs peak torque:"," rated torque is what the motor can output continuously — use it for sustained holding and steady-state loads; peak torque is the short-duration ceiling — use it for start-up, impact, and dynamic swings. Keep ",[275,297,298],{},"continuous operation within rated torque"," and ",[275,301,302],{},"reserve peak torque for transients",".",[290,305,306,309],{},[275,307,308],{},"19.5 reduction ratio:"," the whole lineup uses a 19.5 planetary ratio, trading speed for torque — output speed is about 1\u002F19.5 of motor speed, which is why rated output speed is a uniform 100 rpm. A common ratio means torque scales mainly with frame size, so selection comes down to matching a \"torque tier\".",[290,311,312,315],{},[275,313,314],{},"24–48 V rated voltage:"," compatible with common robot bus voltages and reusable across 24 V and 48 V systems.",[290,317,318,321],{},[275,319,320],{},"Peak phase current:"," reflects the current the drive must supply — larger frames demand more (90 A on the BXI8515-19) — size your power supply and drive headroom accordingly.",[290,323,324,327],{},[275,325,326],{},"Weight and end-effector inertia:"," joints closer to the end (wrist\u002Fhand) should use lighter models; lower end inertia helps dynamic response and energy use — the 5014\u002F5018, as light as 0.5 kg, are built for exactly this.",[20,329,331],{"id":330},"a-three-step-selection-workflow","A three-step selection workflow",[333,334,335,341,347],"ol",{},[290,336,337,340],{},[275,338,339],{},"Set the torque tier:"," estimate the continuous holding torque and peak impact torque in the worst-case pose, then shortlist models — match holding torque to rated torque and impact torque to peak torque.",[290,342,343,346],{},[275,344,345],{},"Check size and weight:"," among models that meet the torque requirement, prefer the smaller-diameter, lighter one — especially for distal arm joints — to cut inertia and overall weight.",[290,348,349,352],{},[275,350,351],{},"Verify routing and interface:"," confirm the hollow bore can carry your cables and sensor wiring (6–10 mm options), and standardize CAN\u002FCANFD communication and bus voltage.",[20,354,356],{"id":355},"how-to-choose-match-torque-to-joint-location","How to choose: match torque to joint location",[287,358,359,368,376],{},[290,360,361,364,365,367],{},[275,362,363],{},"High-torque leg joints (hip\u002Fknee):"," choose the ",[275,366,39],{}," (150 N·m peak) for sufficient support and dynamic torque.",[290,369,370,364,373,375],{},[275,371,372],{},"Primary arm joints (shoulder\u002Felbow):",[275,374,42],{}," (50 N·m peak) to balance torque and weight.",[290,377,378,364,381,384],{},[275,379,380],{},"Lightweight distal joints (wrist\u002Fend):",[275,382,383],{},"BXI5018-19 \u002F BXI5014-19"," (35 \u002F 25 N·m peak), as light as 0.5 kg to reduce end-effector inertia.",[20,386,388],{"id":387},"core-technology-hollow-shaft-dual-absolute-encoders-cross-roller-bearings","Core technology: hollow shaft + dual absolute encoders + cross-roller bearings",[287,390,391,397,403],{},[290,392,393,396],{},[275,394,395],{},"Hollow-shaft planetary reduction:"," the large-diameter hollow output frees routing space for cables, hydraulics, and sensor modules, greatly simplifying whole-robot wiring and increasing joint range of motion; planetary reduction balances torque density with a compact structure.",[290,398,399,402],{},[275,400,401],{},"Dual absolute encoders:"," one absolute encoder on each of the input and output sides measures the true output angle directly, delivering higher closed-loop control accuracy and enabling power-on without homing — the joint position is known at boot, with no zeroing routine.",[290,404,405,408],{},[275,406,407],{},"Cross-roller bearings:"," a single bearing handles radial, axial, and moment loads simultaneously, improving joint stiffness and rotational accuracy — ideal for load-bearing joints.",[20,410,412],{"id":411},"communication-and-control-cancanfd-mit-protocol","Communication and control: CAN\u002FCANFD + MIT protocol",[16,414,415,416,421,422,426],{},"The whole lineup uses CAN \u002F CANFD and is MIT-protocol compatible, supporting hybrid torque \u002F speed \u002F position control for high-bandwidth, low-latency multi-joint coordination on a single bus. On high-DOF robots, pair them with the ",[417,418,420],"a",{"href":419},"\u002Fen\u002Fmotors\u002Fcontrol-modules","PCIE-CAN control modules"," (up to 24 CAN buses, 1 kHz control) for centralized scheduling; the ",[417,423,425],{"href":424},"\u002Fen\u002Fblog\u002Felf3-humanoid-robot-specifications","Elf 3 humanoid robot"," uses a PCIE-CANFD architecture to reach a >1000 Hz whole-robot control rate.",[20,428,430],{"id":429},"validated-on-whole-robots","Validated on whole robots",[16,432,433],{},"The 85\u002F70\u002F50 series has been validated on multiple humanoid platforms under defined test conditions and is used across the Elf 3 joint system, from load-bearing legs to arm manipulation.",[20,435,437],{"id":436},"faq","FAQ",[16,439,440,443],{},[275,441,442],{},"What is the torque range?"," Rated torque 7–40 N·m and peak torque 25–150 N·m across the lineup, covering joints from end-effector to leg.",[16,445,446,449],{},[275,447,448],{},"How do I use rated vs peak torque?"," Select by rated torque for continuous holding and steady-state loads, and by peak torque for start-up, impact, and dynamic swings — leaving headroom for safety.",[16,451,452,455],{},[275,453,454],{},"Which protocols are supported?"," CAN \u002F CANFD, MIT-protocol compatible, with hybrid torque \u002F speed \u002F position control.",[16,457,458,461],{},[275,459,460],{},"Why dual absolute encoders?"," Both input and output sides measure the true angle directly, improving closed-loop accuracy and enabling power-on without homing, which simplifies calibration.",[16,463,464,467],{},[275,465,466],{},"Which model for arms vs legs?"," Use the BXI8515-19 (150 N·m) for load-bearing leg joints, the BXI7010-19 (50 N·m) for primary arm joints, and the BXI5018-19 \u002F BXI5014-19 for lightweight wrist\u002Fend joints.",[16,469,470,471,475,476,303],{},"For selection advice or samples, ",[417,472,474],{"href":473},"\u002Fen\u002Fcontact","contact us"," or see the ",[417,477,479],{"href":478},"\u002Fen\u002Fmotors\u002Fadvanced-motors","joint motors page",{"title":481,"searchDepth":482,"depth":482,"links":483},"",2,[484,485,486,487,488,489,490,491],{"id":22,"depth":482,"text":23},{"id":281,"depth":482,"text":282},{"id":330,"depth":482,"text":331},{"id":355,"depth":482,"text":356},{"id":387,"depth":482,"text":388},{"id":411,"depth":482,"text":412},{"id":429,"depth":482,"text":430},{"id":436,"depth":482,"text":437},"2026-06-20","Compare BXI 85\u002F70\u002F50 joint motors by rated and peak torque, weight, dimensions, encoder design, and CAN\u002FCANFD support for robot joint selection.","md","\u002Fmotors\u002Fadvanced-motors\u002Fall_1.webp","joint motor, hollow shaft motor, planetary gear motor, robot joint module, torque motor, dual absolute encoder, joint motor selection, humanoid robot actuator",null,{},true,"\u002Fblog\u002Fen\u002Fjoint-motor-selection-guide",{"title":5,"description":493},"blog\u002Fen\u002Fjoint-motor-selection-guide","8mhlrQkuLz9pIo9SovFV7N8WPXU-qHm_zc4eBS-NVWs",1789463604995]