Quadruped Robot Dog Endurance Challenge: 67.7% of Losses Are Hidden in Actuators—How Much Can SiC MOSFETs Reclaim from the Joints?
Quadruped robot endurance is not solely limited by battery capacity; actuator electrical loss is a core constraint. KAIST RAIBO2 robot dog full-marathon measurements show actuator electrical loss at 67.7% of total system loss, including 13.3% driver switching loss and 5.8% conduction loss. SiC MOSFETs can reduce driver loss via on-resistance and gate charge, an important device optimization for endurance in 48V bus robot systems.
1. System‑Level Loss Breakdown: Insights from Marathon Field Test
The KAIST RAIBO2 quadruped robot completed a full 42.195 km marathon powered by a single 1930 Wh battery pack, with actual energy consumption of 1280 Wh. Under comparable conditions, the theoretical full‑charge range is approximately 65 kmcdn.herald....
The research team quantified system‑wide energy dissipation. Motor copper loss contributes 40.2 % as an intrinsic motor loss term. By contrast, driver switching loss plus conduction loss totals ~19.1 %, which can be mitigated through power‑device selection and circuit design.
Quadruped robots operate under highly dynamic conditions fundamentally different from constant‑speed industrial AGVs. Joint motors continuously cycle through acceleration, braking and energy regeneration during walking, trotting and posture adjustment. Silicon MOSFETs suffer from body‑diode reverse‑recovery effects and turn‑off tail currents, whose cumulative switching losses become much more severe under dynamic profiles than in steady‑state applications.
2. Two Technical Paths for Loss Reduction with SiC MOSFETs
SiC MOSFETs reduce driver‑stage energy dissipation by targeting both conduction loss and switching loss, to satisfy differentiated requirements of robot joint drives and on‑board auxiliary power supplies.
2.1 Conduction‑Loss Optimization: Graded Rds(on) for Different Power Branches
Hypersemi’s 650 V SiC MOSFET portfolio offers a broad on‑state‑resistance range from 20 mΩ to 540 mΩ, covering diverse current‑level power branches inside quadruped robots.
CM65R380FX100 (650 V / 11 A / 380 mΩ, TO‑252 SMD package) fits gate‑drive power supply, sensor power rails and medium‑low‑power auxiliary converters inside compact joint assemblies. The surface‑mount form factor saves valuable PCB real‑estate within joint housings.
For through‑hole design requirements, pin‑to‑pin compatible CM65R380TFX100 (TO‑220F) shares identical electrical parameters. For joint‑drive branches with higher continuous current, 650 V SiC MOSFETs rated 65 mΩ / 38 A further cut conduction loss as a drop‑in alternative to conventional silicon devices.
2.2 Switching‑Loss Optimization: Minimal Reverse‑Recovery for Dynamic Profiles
SiC MOSFETs feature negligible reverse‑recovery charge and nearly eliminated turn‑off tail current compared with silicon counterparts. In the RAIBO2 electrical‑optimization workflow, engineers reduced gate resistance from 180 Ω down to 10 Ω, lowered switching frequency from 20 kHz to 15 kHz, and minimized parasitic inductance via PCB layout refinement to contain switching losses.
Benefiting from low gate charge and low output capacitance, SiC MOSFETs achieve substantially lower per‑cycle switching loss while preserving control bandwidth, which yields runtime improvements under highly dynamic gait conditions.
Note: Component‑level improvement is only one part of system optimization. Endurance gain requires joint tuning of mechanical design, motor performance and reinforcement‑learning locomotion policies. Power‑device replacement alone cannot deliver full performance improvement.